Sammy:
There is no function in Adagio to restore files. You must do that through Windows by locating the correct ZIP file and extracting the files to a different folder. Be very careful to not overwrite the live files.

But why not just make a "Prior Year" posting to adjust the past year? That is easier than restoring files and, at the same time of course, updates your live data.

Are you using Ledger 8.1 or 9.0?