The cutoff varies every year, It also depends on the factors like Caste category, Home State quota,  Other state quota, caste category etc. It would be tough to tell you the exact but try to score more than 145-150 as a General category to get into NIT Patna. You can also check the previous  year cutoff rank of NIT Patna with the given below link.

https://engineering.careers360.com/articles/jee-main-cutoff-for-nit-patna

Good Luck!