I bought a Apple Watch it’s locked and I don’t know the owner

Recycle it or return it. It will not work for you unless the original owner removes activation lock.

https://support.apple.com/en-us/HT205009

The person that you bought this watch from needs to follow all the steps in this link;

Prepare the watch so the buyer can use it.

If they can't or won't then get your money back or recycle the watch and put it down to experience.