Use the Find My app to mark a missing iPhone, iPad, iPod touch, Apple Watch, Mac, supported AirPods, or iPhone Wallet with MagSafe as lost. In order to mark a device as lost, you must on your iPad.
Tap Devices at the bottom-left side of the screen, then tap the name of the lost device.
Below Mark As Lost, tap Pending or Activated.
Update the information, then tap Done.
When you find your lost device, you can turn off Lost Mode.
Open the Find My app Find Devices on iCloud.com. For more information, see Apple Support article: If your iPhone, iPad, or iPod touch is lost or stolen