Will Arion moderate profile, smooth round, silicone implants, 265cc be too small for me to achieve a C cup? (photos)

You need a formal evaluation by a licensed plastic surgeon and expert in breast augmentations to determine what is best for you and your goals.
Proper breast enlargement is not a "cookie-cutter" procedure where the same technique is applied to every patient. Every woman who comes to my practice has unique needs and different goals for her breast augmentation. As a board-certified plastic surgeon, I always listen carefully to each woman's concerns and thoroughly discuss the key points of the procedure. I also take into account their overall height and weight, the size and shape of the underlying chest and ribcage, the tightness and elasticity of the skin, and the amount of natural breast tissue. Prior to the procedure, we discuss and make decisions regarding location of the incision, whether to place the implant under or over the chest muscle, and what type of implant to use (I offer multiple types of silicone gel breast implants, as well as saline implants).
My experience performing thousands of aesthetic breast surgeries in a wide anatomical range of patients enables me to achieve consistently beautiful and natural results that are customized to each patient’s body type and goals. These results are the product of extensive communication, meticulous planning, and skillfully executed surgery.
I suggest consulting with a board-certified plastic surgeon and expert in Breast Augmentation surgeries. - Dr. Cohen

Dear Berta67,
Breast implant type and sizing selection is a complicated process and requires a detailed consultation that includes a discussion of your goals, a detailed examination, and a lengthy discussion. But the decision will always start and end with the patient. When it comes to sizing, we have all of our patients find 3 photos of their desired breast size. We ask for naked breast photos because clothing can obscure the true size (push up bras). Next, we consult with patients and go over the photos and take detailed breast measurements during a physical exam. Next, we using a sizing algorithm to determine a range of implants that will work based on the exam and the measurements.Lastly, during the operation, we use silicone sizers in the operating room to see how the size actually looks in the breast. We sit the patient up in the operating room, while asleep of course, and compare the sizer result with their desired look photos. If it is too small, we start the process over with a slightly larger implant. We don't stop until we get the perfect match.Of all of my breast augmentation patients, every one of them has been happy with their size due to this detailed and meticulous process. You don't want to invest time and money into a result that is either too big or too small.You should discuss your concerns with a board-certified plastic surgeon and make sure that your surgeon understands your goals.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Based on your photographs, I think that you are starting at a good place and should have a very nice outcome with breast augmentation surgery. My best advice: more communication.
It is definitely worth spending more time (prior to the date of surgery) with your plastic surgeon to discuss further.  As you know, it will be important for many reasons, that you feel comfortable that you and your plastic surgeon are on the "same page" prior to proceeding.
One question that might be helpful for you to consider: would you be more disappointed if you are slightly too big or slightly too small after the breast augmentation procedure?
Ultimately, careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) will be critical.
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. For example, I have found that the use of words such as “natural” or "C cup” etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup size may also be inaccurate. Again, the use of computer imaging has been very helpful during the communication process, in our practice.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery, after the use of temporary intraoperative sizers.
I hope this helps. Best wishes for an outcome that you will be very pleased with.