With the exception of the 2024 models of iPads Air and Pro which only have an eSIM, earlier WiFi+Cellular models of iPad have a physical SIM slot for a DataSIM.
Moving a compatible SIM between iPads is simple - but clearly Cellular service using the SIM will only be available for the iPad in which the SIM is installed.
Remove or switch the SIM card in your iPad - Apple Support
iCloud is linked to your AppleID. All devices that are signed-in to iCloud with the same AppleID share the same iCloud storage. As such, data stored in iCloud is available to all devices using the same AppleID.