Hey.

The National Law Universities or NLUs do not provide the course of 3 year LLB. These NLUs only provide 5 year Integrated course of law that combines an undergraduate degree with law like BA LLB, BCOM LLB, BBA LLB etc. The top government  colleges for a 3 year  LLB degree are-

Delhi University

GLC Mumbai

ILS Pune

Panjab University, Chandigarh 

Banaras Hindu University

Bharatiya Vidyapeeth, Pune

Osmania University, Hyderabad 

School of Law, IIT Kharagpur

Best of luck