If your nipples are facing forward and are above the level of your inframammary crease, then you may obtain a nice result with augmentation alone, but may need large enough implant volume to adequately "fill" your loose breast skin. You should first have a desired size in mind, rather than asking a surgeon what size you should be. Then, an experienced plastic surgeon can determine by examination, careful measurement of your chest and breast dimensions, and talking with you about your desired outcome, just what size and profile of implants will work best to fulfill your goals in accordance with your anatomic requirements (with or without a breast lift).
You should read my article (on my "About" page) "What is the Right Breast Implant Size for You?" for more information about this critical topic. You can also read much more information at my website link below.