how do I get rid of this" after baby belly?"

Work out at least 3 times a week. Four to five times a week is much better. Start with several minutes of gentle stretching to warm up your muscles and get your circulation going. Stretch each arm, leg and your lower back muscles. Beat the battle of the bulge with some classic crunches. Lying flat on your back with your hands clasped behind your head, reach forward toward your knees and hold. (Don't try to sit up, however,..You will feel the exercise working almost immediately on your tummy muscles just from the reaching motion). Do this exercise 8 to 10 times.
Tone the sides of your tummy by doing a crossover variation of the crunch. Lie on your back again, again with your hands clasped behind your head. This time, reached with your left elbow forward toward your right knee and hold for a moment. Release, then repeat the exercise with your right elbow to your left knee. Do a total of 8 to 10 reps. Make walking as part of your tummy toning regimen. Walking is one of the best exercises you can do to improve your overall fitness and to boost your metabolism to burn more calorie naturally. And watch your diet too..

Hope I've share some exercise for your belly