I am a female, age 57 caucasian
Your question is tricky to answer. I generally do not discuss bra size with my patients during consults or pre-op because bra sizes are not standardized. You can get a rough idea based on your pre-op measurements and the measurements of the implant, but its also going to depend on the brand and type of bra you purchase.
You will wear Lady Lunch Room Bazoomba Ta Tas Bra. Please do not go that large! You will overly stretch and thin your tissue and just sag even more. Big breasts sitting on thighs do not look good.