So the backup I linked requires you to install a specific version of java, then install the backup package. Let's not do that.
Here is a bot you can invite Ant: https://xenon.bot/
It will allow you as an admin to do backups, and then make a new server and restore to there. This bot will also allow scheduled backups to be set up so you always have it available.
The free version allows:
Backup channels and roles
Up to 25 backups
Keep 1 interval backup per server