How do I find my uncles Birth Certificate?
The answer to that depends greatly on where and when he was born. Some helpful guidelines for the United States can be found in this wiki article: https://www.familysearch.org/en/wiki/Locating_United_States_Vital_Records
Procedures for other countries will be different, but the wiki has advice specific to many countries for locating vital records; just search the wiki for the country you're interested in. You can also search for states, counties, and other regions for specific guidance.
Note that privacy laws (which vary widely by jurisdiction) place restrictions on when records can be obtained, depending on when the person was born or died, or how you are related to them.
@paulette982 If you give us the location and date someone will likely be able to provide you with an exact answer.