Dear Omkar,

After you B.tech you can apply for GATE entrance exam for your PG course. 

To check all the entrance exam for M.Tech you can refer below link

https://engineering.careers360.com/exams/PG

Based on 2017 cut off in order to take admission in COEP you should try to score more then 150 marks in MHT CET in general category.

Cut off marks varies as per the branches. For top branch like CSE you need to score 180 marks in MHT CET. 

Good Luck!!