Answer: Any country that considers 16 to be an adult - like lots of places in Europe and maybe even Mexico, Brazil etc
Explanation: however, I would not do it at 16 - your face and body will change a lot ! I used to want to have a breast augmentation when I was 18 because I got picked on a lot for having small breasts. Now I am a DD and am beyond happy I didn’t get the augmentation. I would wait till at least your earlier 20’s or so!
Hoped this helped a little bit