To migrate an Azure file share backup between vaults, you cannot simply "move" the backup data. You must stop the backup in the source vault (Vault1).

1. Backup items: You must navigate here to locate the specific file share and "Stop backup." If you intend to delete the old data to avoid costs or conflicts, you must choose the option to "Delete backup data."
2. Backup policies: While the policy itself isn't "changed" to move the vault, in the context of preparing Vault1 for this change (and potentially cleaning up or dissociating the resource), the policy governing that specific share must be managed or the share must be removed from it to break the link between the resource and the vault.

Microsoft Learn (Official Azure Documentation): "Back up Azure file shares" section on managing backups. It specifies that to change vaults, one must stop protection in the current vault before re-registering the storage account in a new vault.

Microsoft Learn: "Delete a Recovery Services vault." This documentation details that a vault cannot be deleted or resources moved unless all Backup items are stopped and deleted.

Microsoft Azure Documentation: "Common questions - Azure Files backup." Specifically addresses moving backups between vaults, stating it requires stopping the backup in the source and starting fresh in the target.

Microsoft Learn: "Manage Azure file share backups." Section on "Stop protection for an Azure file share" highlights the use of the Backup Items menu to initiate this process.