Hello Yogesh,

there is nos pecific syllabus in website, yet, everything of 10+2 syllabus + Number Theory+ some extra theories in topics like Geometry, Algebra, Combinatorics , Calculas etc are assumed to come in the examnation. So prepare accordingly

here are some lins that you can use to prepare for

•  https://engineering.careers360.com/articles/isi-sample-papers
  

• https://www.isical.ac.in/~admission/IsiAdmission2017/PreviousQuestion.html
  

• https://admission.aglasem.com/isi-kolkata-admission-sample-papers/
  
• https://www.isical.ac.in/~admission/Syllabus-And-QP.html
  
• https://www.raoiit.com/answer-key-solutions/isi-exam-paper-solutions.php
  

hope these link help in your preparation.

All the best for the exam.Hope you do well in it