How long would it take for me to get abs?
I’ll do about 500 crunches per day with no stops..okay maybe one 30 second one.
I am 16, 5’5”, and weigh 100 pounds.
How long do you think it will take for me to get abs? My stomach is pretty flat but has no defined abs

You already have abs, you just can’t see them. Try to do more crunches than sit-ups as these will work the actual abdominal muscles not the muscles behind them that make you sit right up.
Gain some weight. At 100 pounds you’re under weight and won’t have any muscle tissue no matter how much you exercise. Muscles contain about 5-10% protein 45% carbohydrates and 45% water. Imagine they’re like little collapsible fuel tanks, without any fuel in them they stay small and under-inflated. A balanced diet slightly biased towards protein and good quality carbs will help fill them out along with all the other muscles.
Good luck