Hi Sush,
Post pregnancy tummy is a very common problem associated with mothers. Post pregnancy belly is a result of more accumulation of fat around the belly and the loose and weakened muscles and skin at lower belly. So to tone up this part ,resistance training exercises plays an important role to shape up your muscles and skin to gain a toned look. Resistance training exercises like Reverse crunches, leg pushs, Leg cycling, Leg lifts , Reverse crunch with medicine ball, etc. We need to do these exercises atleast for 25 min so as to get better results. Also, we need to look into our daily diet like avoid eating junk food and try eating healthy nutrious food. Again, try being active as much as possible which will help to burn calories frequently and also breast feed your baby which will help to reduce your pregnancy fat.