Candidates who have passed 10+2 or equivalent level exam with science stream in 2018 or 2019 are eligible to apply for admissions. Candidates will be admitted to IISER only through following three channels.

Kvpy

Jee and

Scb

In your case SCB applies and you will have to give the IAT entrance test. You can check the cutoffs for the entrance test eligiblity om the official site of iiser below.

https://www.iiseradmission.in/eligibility/