I'm wondering what cup size 400cc would give me? I forgot to ask my surgeon (Photo)

It is always good to think of implants in terms of frame rather than cup size. Patients often think in terms of cup size when considering augmentation. Unfortunately, devices are sized in terms of milliliters (cc) of volume. This can lead to some confusion when sizing. Additionally, it is important to remember that cup size itself is not standardized with variations from one manufacturer to another. Unfortunately, as many women can attest their cup size in an industry leader such as VS is not necessarily transferable to another brand.
Another point which is often under appreciated is that of anatomy and starting point. Any implant will add volume to the volume which is already present. The implant is additive. A particular volume will not necessarily confer the same cup size to different patients (often times it will not even confer the same cup size to different breasts in the same individual...remember they are "sisters" not "twins"). 
A general rule of thumb is that 125cc can represent somewhere between 1/2 to a full cup size increase. Smaller volume differentials (25-50cc) are typically less consequential representing a volume change of less than a shot glass. However, I have found these numbers, at least anecdotally, to be of little help. Patients often present with notions/goals which do not correlate with these sorts of sterile volumetric assessments.
When sizing patients, there are a number of useful tools including:
-3D imaging (has the added benefit of offering a volumetric analysis of the pre-operative breast)
-Breast sizers (rice bags)
-Goal photos
I also recommend that patients commit to a particular look rather than a cup size. Once a patient settles on a look that pleases them the overall cup size increase becomes less relevant.
With regards to your specific question, it is important to understand the differences between profiles. For a given volume, a higher profile device will be narrower and project more, whereas as a moderate or lower profile device will be wider and with less projection. A high profile device will allow for greater volume and more projection. In my experience, on an frame like yours I would favor a higher profile device. I would suggest a conservative volume moderate + profile device or the equivalent high profile device (same measures, slightly higher volume). If you do opt for a higher profile device, it is important to remember that the increased profile comes with an increased projection.You are seeking a "natural" look. The safest way to achieve this is by staying within the anatomical bounds established by your BWD. Exceeding these measures leads to greater lateral show and greater risk of the dreaded "fake" look.
As always, discuss your concerns with a board certified plastic surgeon (ABPS).

Cup sizes are not standard across bra makers, and implant sizing is NOT based on height, weight, BMI, or capsize.  This is something you will need to do IN PERSON with an experienced surgeon to determine what works well for you, and to get advice about if what you like is possible and what to expect with regards to results.  Be sure to discuss your goals and concerns with your board certified plastic surgeon and consider the pros and the cons. Be certain your surgeon is properly certified.  I've attached a link where you can start your search.  

Hello and thank you for your question. You are a great candidate
for a breast augmentation.   A 400cc implant may work for you based on your goals and picture.  The size, profile, and shape of the
implant is based on your desired breast size/shape, your chest wall
measurements, and soft tissue quality.  This decision should
be based on a detailed discussion with equal input from both you
and your surgeon. 
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon