Howard Miller

Not at all. I'm completely unfamiliar with cPanel and what it can do (although I get the general idea).

Forget about all that .sql.gz stuff. Just run the command...

mysqldump -h example.com -u myusername -p'mypassword' -C -Q -e --create-options mydatabasename > moodle-database.sql

....this generates moodle-database.sql which you can copy across to the new server and use to create the new Moodle database. I've never used cPanel but I would be surprised if it didn't have an option to import an SQL file.

There's nothing special about cPanel / not cPanel. The full story is here - Moodle_migration.

If you have any specific questions or concerns, ask away

Moved

Your biggest problem is that XAMPP was never designed or intended for "production" use. Even with a properly configured system 3,000 students starting a quiz at the same time (if that's what you mean) is a VERY big ask. That's going to require a substantial system (probably load balanced) configured by an experienced Moodle administrator.

So, a big system like that running on XAMPP is probably never going to work.