At first lots of congratulations for your results .
I . I can predict your score is about 20 and your All India rank is about 5.5-6 lakhs .According to trends of previous years and this year's JEE MAIN cut off I am afraid to inform you that your chances of getting admission into colleges NITs and IITs are tough. However You can try in state level counselling and private colleges .One thing is important that admission in ST category entirey depends upon that particular category rank , not the All India rank. So you must mention that sp we can help you precisely.
you can check previous years cut off
https://engineering.careers360.com/articles/jee-main-cutoff-for-top-nits
check your chances here
https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer

Best Wishes.