From where are you attempting to move your files - and to where?
Move is generally available within a filesystem - such as within iCloud folders or locally on your iPad. By contrast, in some circumstances you may not be able to directly Move between storage providers (e.g. iCloud and Google Drive). Instead, you may need to Copy - and then [if required] Delete files from the original storage location/provider.
It is perhaps worthy of note that a copy/delete action is sometimes safer than a move operation - as, if an error were to occur during a move, you may experience data loss or corruption. With copy/delete, the original file(s) remain accessible until they are manually deleted.