Aditya, you are probably very young and since Indian Govt. to date have taught false history in their schools, your ignorance is perhaps excusable. (I was brought up in a British colony in Africa and so had an excellent education!)
But as an adult it is time for you to study history from sources other that school-textbooks and understand why there are Hindus in Pakistan.
Most of the Hindus have been forced to convert so that they could hang onto their ancestral properties.
Jinnah personally asked the poor landless hindu scavengers not to leave Pakistan as their labour was needed to keep the then capital Karachi clean!
Jinnah famously promised to respect all religious minorities. He was personally quite irreligious and only desired to have Muslims as bosses - the idea of Hindus as masters was repugnant to him - hence the need for his own state!
