Archival search

Hello Everyone,
I am trying to find information about doing an archival search in the Ukraine. Briefly, my father was born in a former Romanian village which is now the Ukraine, and I am trying to find his birth certificate, as all his documents were lost when he fled in 1939.

Does anyone know how I could go about doing an archive search from abroad, or if it would even be possible if I travelled to the Ukraine? The village no longer exists, so I'm not sure which area I should even broach for an archival search. The village was south of Odessa, so perhaps the archive there.

Any advice would be greatly appreciated.

Thank you