Dear Shivankit,
An LLB is a degree awarded to individuals who decided to pursue a deeper understanding of the law.
A program in criminal law focuses on enhancing pupils knowledge of the legal system, best legal practices and criminal behavior.Students who pursue this degree tend to possess a firm understanding of legal and criminological principles.
Firstly you need to get bachelor degree in law and then pursue an master degree in Criminal Law specialisation.

I hope this information helps you
All the best