How to get birth certificate of 30 years ago?

I was born in 1980 at Nallasopara Dist Thane. After 1.5 years My mother passed away. Then We shifted to South Bombay. SInce then we are staying in South Bombay. Now My father is also passed away. Now i need a birth certificate. Please tell me the procedure to get birth certificate from erstwhile Nallasopara Gram-Panchyat.