Ok, so I did spend some time searching about this & found that, skype history is saved in microsoft servers till 30 days after one uninstalls skype without saving the old chats(History). So if I download it again within 30 days I need to sync my account to the server get all the chats back.
Here is my case.
I had uninstalled skype without actually choosing any option of saving history. But if the history is automatically saved in any folder then I think I have the chance of getting it back.
But I had formatted my laptop twice after that but every time I took back up of C folder (Windows 7). So incase if the history gets save automatically in C folder then I can some how manage to get the chats back.