Can I go from a B cup to a C cup with 350cc or 375cc saline implants under the muscle? (photo)

I would agree with your plastic surgeon that a breast lift will be helpful in your case. Exactly what type of breast lift I would recommend to you would be based on physical examination.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. I have found that the use of words such as  “natural”  or “B cup, small 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.
 The use of computer imaging technology may also be very helpful during this communication process.

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.
I hope this (and the attached link) help.

Cup sizes vary widely with different bra manufacturers. In our practice we use a number of techniques including 3D imaging to assist patients with figuring out the right size to help them achieve their goals. One useful exercise for your particular question is to find a "C" cup bra without a lot of padding that you feel would suit your body and you would like to fill out. You can then use a kitchen measuring cup to measure out different amounts of rice which you can place in a small flexible bag (an old pair of nylons works perfectly for this). The amount of rice (in mls or ccs on the metric side of your measuring cup) that allows you to fill this bra comfortably will give you some idea of the size of implant that may work well for you.Be sure to arrange a consultation with one or several board certified plastic surgeons to help find which option is likely to work best for you.