Have you tried a 500cc implant in a stretch bra, so you can get some idea of what size breast mound it will create when added to the breast tisue you already have? Although this may not be absolutely 100% accurate, it is better than talking numbers without having any visual information to associate with it. A 500cc implant is pretty large, but that may be what you are looking for. In addition to having patients try sizers on and choose a size or range of sizes TO AIM FOR, we try the sizers in the breast pocket during surgery and get a more accurate picture of whether that size will work. We will have discussed with the patient preoperatively what contour goals they have (how much upper pole fullness and how natural or unnatural a contour they desire), and patients can bring in photos to help us understand what breast shapes they like and are seeking. We may aim for a chosen size, but patients give us permission to go down in size if the implant is too tight and the resulting contour will not be what they are hoping for.
By the way, your breasts look somewhat ptotic (hanging down with a low nipple position), but it is hard to tell from a photo without examining you where your nipples are in relation to the level of the underlying inframammary crease. You also appear to have a left nipple lower than the right, with little to no skin visible on a frontal view of the breast below the left areola. Please be aware that implants fill out the breasts, they do not lift them. If your breasts are hanging too far below the crease, they will hang off the implant. If the nipples are too low, they may reside at the bottom of your breasts and point downward. If you have nipple asymmetry preop, this will persist postop. The only procedure that addresses these issues is a breast lift. Since you do not mention a breast lift, I am assuming that this has not been discussed. Just make sure you understand what augmentation does and does not do, and that your expectations are in line with what can be delivered.