The best and easy solution to restore your WordPress site from an old backup is to make a new and normal WordPress installation of the latest available.

Next, you need to copy the wp-content folder from your backup and past it inside your local website root of that new installation, beside wp-admin and wp-includes folders.

Once finished this step, you pass to import your database sql file from your phpMyAdmin platfom. Your (zipped?) backup should include a SQL file that contains all your database content.

After that, make sure that your database name is the same on configuration file wp-config.php to connect your WordPress with the database correctly. You have to update too your database password if exists.

The next and final step is to edit your admin password (if forgotten) directly from the database. At this point, theoretically at lest, all is done, and next you can access without problems to your website dashboard.

Please let me know if you have any inconvenient ??