if we go through the latest cut-off of 2020 then it shows that the closing rank for SC category was 29 for CSE branch in IIT Bombay . It is little bit difficult to tell you about exact marks to score because for JEE-Advance no maximum marks are fixed but yes with regards to JEE-Advance 2021 if you secure your AIR in JEE-Advance under top 40 in SC category then there would be good chances for you to get CSE branch in IIT Bombay .

You can check out the latest cut-offs from the link given below :-

https://josaa.nic.in/Result/Result/currentorcr.aspx

Note that the above prediction is made on the basis of latest cut-offs available on official website of JOSAA and the cut-offs are bound to change every year depending upon various factors such as the number of candidates appearing in an examination, the number of candidates qualifying an examination, difficulty level of the paper, and so on.

To have a list of all those colleges which you can get based upon your JEE-Main score, category, and state you can use JEE-Main College Predictor :-

https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer