I found apple watch how can i return it to its owner can you help me with that please ?

There isn't a way to return the watch. Apple doesn't assist in this. Turn it over to local police.

ASC - Late 2012 Mac mini, macOS 10.15; Watch, series 3 cellular, watchOS 6.0.1; iPad Air 2, ipadOS 13.1.2; iPhone 8+, iOS 13.1.2; TV 4th Gen, tvOS 12.4.1;  HomePods, audioOS 12.4 and Airport Express w/ Airplay 2

Turn it over to the police.