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Locate a device in Find My on iPad - Apple Support
Here is Apple’s advice for lost or stolen devices:
If your iPhone, iPad or iPod touch is lost or stolen – Apple Support
Use the Find My app to locate a lost or stolen device – Apple Support
If the Find My iPad feature was enabled prior to it being “misplaced”, then if active, you would stand a good chance of locating it.
However, if the feature was not activated prior to being misplaced - or the iPad has been inactive for more than 24 hours, the last known location will not be available - and the opportunity to use technical means to recover the iPad have been lost. The Find My service can only be activated from the device itself while it is in your physical possession; once lost or stolen, it is too late.
If the iPad was a WiFi+Cellular model, ensure that you have informed your Cellular Carrier if applicable - as your Cellular service may need to be suspended and/or block your IMEI. Also, as appropriate, inform your local authorities of the theft.
To find your iPad serial number and other information, simply sign-in to your Apple Account (formerly known as your AppleID) from any computer using a web-browser:
https://appleid.apple.com
Having signed-in, open the Devices tab. Here you will find an entry for every device associated with your AppleID; tap the related entry to see full technical details of the device - including Serial Numbers and IMEI/MEID of Cellular devices.
AppleCare
You should note that an AppleCare+ plan for iPad does not provide any coverage for loss or theft. This differs from AppleCare+ plans for iPhone which offer an optional extension (for an additional premium) that does provide coverage for loss/theft.