You can easily create a backup of your Pligg website by simply downloading all of your Pligg files via FTP and export your database. You can access your Pligg files and download them via FTP following the instructions at:
https://www.tmdhosting.com/tutorials/video/ftp.html
Your CMS MariaDB database can be easily exported through cPanel by accessing phpMyAdmin. Simply select the database you want to export and use the Export option to download a copy of it.