You can calculate your Body Mass Index to see where you are in relation to others.
As to when you'll notice a 6 pack, it varies. For one, you can't spot reduce.
A more important consideration is that you are 16. You are still growing and developing. Testosterone will change your body. You've no doubt noticed some signs, pubic hair, genitalia growth, etc. It will also make you more muscular.
Eat a balanced diet and continue what you do. Remember too, muscle weighs more per volume than fat.
Hope it helps.