Hello prashi,

Nirma university take admission on merit basis, it gives 50% weightage to 12th result and 50% weightage to NATA exam score. So you have to take NATA exam to get admission for B.arch in nirma university. But with jee main score you can get admission in btech in this college. Go to the below link to know the cut offs of different branches of last year-

http://www.nirmauni.ac.in/itnu/btech_AI_Cutoff

All the best