The first page in the MMS Backup documentation for restoring is called Restore from a Stored Snapshot.
The first step in that is:
1. Extract the files from the .tar.gz archive created by the backup service.
Yet there's no mention of where to actually get this tar.gz archive, which can be rather confusing.
Strangely, the page for Restore Replica Set from a Point in the Last 24 Hours does include this information.
It would be good to get this information on the Restore from a Stored Snapshot page as well, particularly since it's the first link in that section.