I appreciate your question.
It depends on your chest wall measurements and existing breast tissue as implant size does not accurately correlate to a bra size. It also depends on the brand and style of bra you wear as size varies from manufacturer to manufacturer.
The best way to assess and give true advice would be an in-person exam.
Please see a board-certified plastic surgeon that specializes in aesthetic and restorative breast surgery.
Best of luck!
Board Certified Plastic Surgeon