If you need to check the installed version of MySQL or MariaDB on your server, the easiest way is to to open a SSH session and then run the command mysql -v and then record the version returned by MySQL/MariaDB.

The next way to check is from the MySQL/MariaDB shell. From your server, issue the command mysql -u [username] -p and then enter your password when prompted. Then run the command show variables like '%version%'; and then record the version returned.