Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Presumably the type of account configured in Outlook was pop mail?
That being the case you should have copied the pst files (with Outlook closed) to another location.
And presumably you have no other data backups.
So how exactly did you backup the OL data/folders?
If Outlook is currently functioning, and what you had done previously had simply copied the folders to the external what type of file is shown in your documents location, an eml file or?