Which is better substitute of mothermilk ... Is it cow milk or formula milk ...

I would say formula milk because it is formulated specially for children. You can try Dumex Mamil Gold. It is blended with its patented prebiotics which is good for a healthy gut and digestive system. It also has more DHA and there is no sucrose added. Dumex sample available in their website http://www.dumex.com.sg/requestsample