Good first step.
Migrating from User to Service install on Windows are currently the latest directions for that.
That won’t know where your old databases were. It will assign new paths. Best to move old.
You can adapt the directions if you like, e.g. copy the old DBs to what Database screen has.
Direct restore from backup files
To restore files from the backup, Duplicati needs only to know how to access the files and the encryption passphrase (if any).
Is that what you mean? There’s also: