Help me locate my watch apple series 9 please

Here is: If your Apple Watch is lost or stolen - Apple Support

You can use Find My to try to locate it, as described there.

If the paired iPhone is nearby, you can use the Watch app to (try to) locate the paired Watch. (Tap all watches, tap the information ℹ️ button for the missing Watch, tap Find My Apple Watch.)

To be located, the Watch must be functional, have sufficient battery capacity, and communications.