Hello!
Your admission through NATA is based on your merit system. Divide the NATA score by 4, and your CBSE result by 2, and add them to find your merit out of 100. Normally colleges accept a student who has 60+ merit overall, and sometimes colleges even go for lower merit. Here's a list of colleges that accept NATA scores and their cutoffs:

https://engineering.careers360.com/colleges/ranking/2018/top-engineering-colleges-in-India-accepting-nata-score?page=1

Good luck!