Can I restore a MySQL table from a file (non-sql) backup?
Your best solution is going to be to install MySQL, stop the service, then completely replace the entire "datadir" with the one from the backup, then cross your fingers before restarting the MySQL service.

The datadir is probably the folder you found in xamppfiles/var/mysql; that sounds right but I don't use XAMPP to know for sure. You can open up the command line client and issue the command SHOW VARIABLES LIKE "%datadir%"; to confirm the proper path.

You can't simply restore the parts of what are missing alongside the existing structure, because you also need the information about which users have access to the tables and other metadata that isn't stored directly in the individual database folder. Restore the entire folder so you get all the correct metadata, database and table structure and data, and permissions.

This is a bit beyond the scope of what MySQL is meant to do, so success is not guaranteed (proper backups usually involve making a .sql file export, which you can do from phpMyAdmin or the command line; I use the 'mysqldump' command line client).