As Paull Said :
Connect your iPad to your iMac/MBP/MB/etc using a lightning cable.
Open Finder, click on your iPad's name.
Click Trust on the iMac/MBP/MB/etc
Tap Trust this Computer on your iPad and enter your PIN as required.
Open the Sidecar preference pane.
Your iPad should be available as a Sidecar device.
But this works only with USB-C cable connected.
Nacer
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