Hello panu singh  ,

first of all you need to score atleast 75% in 12 th boards or be in top 20 percentile in your board. Make sure you are in top 20 percentile.

And now coming to your rank then with this rank getting a NIT or IIIT is very difficult 

So, you must try for private colleges of Kolkata and bangalore who take form JEE mains.

To know what all colleges take through jee mains in which you can get, follow the following link:

https://engineering.careers360.com/colleges/list-of-engineering-colleges-in-kolkata-accepting-jee-main

https://engineering.careers360.com/colleges/ranking/top-engineering-colleges-in-bangalore-accepting-jee-main-score