How to report my stolen Apple Watch?

Apple doesn't get involved in lost or stolen devices. You report theft to your local authorities.

See this link --> If your Apple Watch is lost or stolen - Apple Support

You contact the police and File a report with them.

Apple does not take reports of stolen or lost devices. Not sure what the updater requirement has to do with anything though.

If you want you can try to track it by following the steps here: link-> If your Apple Watch is lost or stolen - Apple Support