As from last year board Mark's are not added for making jee rank,So your rank will only depend on Jee score, with 120 score and SC Category you will easily get an nit

Hello Rupali
Considering your category - SC, your marks - 120 and the previous years' trends and cutoffs for admission into NITs, you should be easily getting admission into an NIT.
All the best ! 

Respected mam,

if you are able to get 120 marks surely you can get NIT since you category is SC it would be easier to get NIT.

Thank you.

If you are able to achieve 120 marks in JEE mains you will easily be able to clear the cutoff for general has well so you will be qualifying using mains and using a category rank and your and the benefit for your category you will easily be able to get the Nit you want.
Wishing you best of luck for the future.

Hii Rupali.Hope you are doing good.Firstly let me clear you one thing.The inclusion of board marks in JEE Mains has been removed.So no need to bother about it.According to me for SC cutoff this year would be around 75.So I think you will get NIT.If you have any doubts please feel free to ask me

Your 12th marks matter only for becoming eligible for NIT, IIT etc. 12th marks don't add up to your JEE score.
However, 120 marks should be enough to get a seat considering your category. You will qualify JEE in general quota but you would get seat only through your category.
Best of luck.