Sorry to hear that your iPod classic was stolen. If you registered your iPod with your Apple ID, you can look the serial number up in your Support Profile:
If you have lost or found an Apple product, please contact your local law enforcement agency to report it. Although Apple does not have a process to track or flag lost or stolen product, you can use My Support Profile to find a list of serial numbers that have been purchased or registered with your Apple ID.
You can find the full article here:
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