350 cc's equal what 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.The key to obtaining a natural result is to stay within the parameters defined by your BWD. This will ensure that you avoid the dreaded "fake" look. 
With regards to your specific question, it is impiossible to determine what cup size 350 cc will deliver without knowing the starting point. On a small breasted individual 350 cc could be as small as a B. While the same implant in a large breasted individual would be significantly larger.
As always, discuss your concerns with a board certified plastic surgeon (ABPS).

hello thank you for your question and provided information as well..Based on your question, it is difficult to say that size is, because it depends on the thoracic box, the breasts, the size of the patient, ect, it is difficult to guide the patient without a photo.my recommendations that you go to consult with a certified plastic surgeon so you can talk about your doubts.

There is no direct correlation between cc's and cup size.  A 350cc implant in one patient may make them two sizes bigger, and in another possibly 3.  I would try to get a 3D image done and/or sizing to determine your optimal size. In my practice this usually get patients dead on to what they want.