Many ways we can find the serial number of AirPods
1. You can find the serial number of AirPods on your charging case
The serial number xxxxxxxx is on the underside of the lid of Your AirPods
2. AirPods are connected to your iOS device then go to Settings -> General -> About -> AirPods
3. If you have the original packaging, you can find the serial number next to the barcode.
You can also find the serial number on the original product receipt or invoice.
You can check the Airpod is original using the serial number using the Official Apple website. How to Check AirPod is Original or Fake