How many CCs of Natrelle Soft Touch to get from my before to the after photo? (Photo)

Choosing an implant size/style is an important decision which is best made in concert with your surgeon. Ultimately, options are based on a number of factors including:
-Chest dimensions: This point is crucial as the width of your breasts defines the available "real estate" on which the foundation of your augmentation is built. This "foot print" is the absolute limit with which you are dealing. Too "large" is not so much the risk as too "wide." You cannot build a 3 acre mansion on a half acre plot. An implant which is too wide (exceeding the available space on your chest) will generally over hang laterally making it more noticeable and occasionally contributing to discomfort and nerve symptoms (numbness or tingling). This will also contribute to a more unnatural look.
-Tissue quality: This relates to size in the sense that the implant will be suspended by your tissue. Too large an implant may place took large a stress on these suspending tissues leading to healing problems in the short term and bottoming out in the long term.
-Patient desire (what is the look you are hoping to achieve?)
My role as a surgeon is to manage expectations and guide you towards a prudent choice which can satisfy these reasonable goals. Often times, a surgeon can guide a patient toward a size/cc range and patients will make determinations on implant style/profile. Patient seeking more or less projection, or seeking a more pronounced or subtle upper pole volume increase can be guided toward an implant which will help them best achieve their goals. Additionally, technique variations (sub muscular vs. sub glandular) can also aid in obtaining the look you desire.
There are a number of tools available to help guide patient/surgeon decision making including sizers, 3D imaging and goal photos. Each modality can help better communicate your goals to your surgeon and vice versa.
Ultimately, it is important to not marry oneself to a particular "cc" as oppose to a particular "look." Communication is key as you and your surgeon create your custom surgical plan.
With regards to your specific question, without an exam/measurements it is difficult to offer a volume recommendation. Based upon your photos alone, you might want to consider a HP implant in order to maximize the volume for a given breast width.
As always, discuss your concerns with a board certified plastic surgeon.

After I measure and discuss goals with my patients, we then look at pictures of women (my patients) with similar measurements. They also get to see what they would look like when the breasts have fully dropped and fluffed and in clothes. You get to see actual results and the surgeon's experience and not a virtual idea of what can be achieved. Women tell me that this process is very helpful in determining what is right for them. Dr. Ted Eisenberg, Board Certified Plastic Surgeon and Author. RealSelf Distinguished Hall of Fame Inductee. Philadelphia, Pa., USA

It looks as if you like a nice full appearance to your breasts. I wouldn't focus on the actual number of the implant but simply have the surgeon create a pocket and select an implant to maximally fill the breast pocket and that will get you that look.

I still use a sizer after making a pocket and then for those patients who would like to be full I fill the sizer to the maximum fill that perfectly fits the pocket (think hand in glove) and then select the implant to match the sizer. It is a simple, consistent way to get the shape and size you desire.