When I used to be 21 my belly was flat now it looks sticking out when I relax it , my abs pop out if I flex is this normal and what can I do to make it flat and my abs show?
Yeah it's normal, it's determined by how much bodyfat% you have, muscle mass and by your genetics. You've gained fat since you were 21 and are now "skinnyfat", no muscles with some extra fat, though your physique is still within the healthy and normal spectrum.
Some advice if you want to improve aesthetics: A classic mistake would be to panic now and start dieting to lose that bit of extra fat. If you do that you will not look much better even though you have abs, because you will just look underweight.
A smarter decision would be to do weightlifting or calisthenics while focusing on gaining weight, not caring about the extra flab you've gained. I promise you this route will make you feel much better as you will look stronger and fill out t-shirts better. Then after like half a year or longer of training you could decide to cut down the fat. To get those abs back ;)
If you work abs with heavy weight, that muscle will get bigger.
If you want a 6-pack, the trick is light weight with high reps.
Check out The Rock just standing there. No abs.
Now, check out The Rock in a laugh, flexing those abs.
So, high reps with low weight.
Also, it looks like you have a relatively high percentage of body fat to muscle mass, so you might want to consider eating healthier. Less fats and sugars. More protein and complex carbs.