Re: "How to move Pages documents from On My iPad to iCloud Drive:
Pages Location : How do I move the Pages location from "on my iPad" to " iCloud Drive " ?"
Seems it is not safe to do that.
Reminder: You can add the Pages files to iCloud, yet if you remove them from iPad they will also be removed from iCloud. ie: If you delete (or add) files from iPad, they also delete (or add) on iCloud.
Seems as iCloud is mainly for sync of files across devices, files in iCloud must also remain on the iPad.
You can however: Set up iCloud for Pages on all your devices - Apple Support
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Else: If you want to store Pages files somewhere else than on the iPad:
You might want to buy an external storage device such as a USB drive.
See how to: Transfer files from iPad to a storage device, a server, or the cloud - Apple Support