Welcome to the community!
Sorry to hear you lost your iPad. Firstly, to clarify, is your iPad specifically covered by the Device Protection? The protection only covers one device at a time and if you also have a protected phone, the coverage won't extend to other devices unless they are specifically covered.
In which Province do you reside? You should note that accidental loss coverage is not available in Québec (see here). If you do live in a Province with loss coverage, you would need to start a service request. You should be able to start the process via My Account.
You should note that there will likely be replacement processing fees and you must file your service request within 60 days of losing your iPad.
Hope you are able to find your iPad and hope this helps 😀