Backup/Restore was completely overhauled in FreePBX v15 which introduced the Filestore module. Legacy versions of Backup/Restore have the management of backups and storage options all under the same module. It’s even in the current documents and why there is a FreePBX 15+ document and a Legacy document.
Here is the legacy documentation for Backup/Restore:
Using the Backup module (Legacy) - PBX GUI - Sangoma Documentation (atlassian.net)