I don't recommend backing up via the forum, it's going to take way longer than how it would be if you where to do it via MySQL directly through the command line (via SSH for example).
Also, all the data is would be text, so if you have it compressed (tar or gz for example) it will be tiny.
The command to create a backup of a mysql database:
MySQL Export: mysqldump -uuser -ppass db > db.sql
MySQL Import: mysql -h localhost -uuser -ppass db < db.sql
Please note that the -u -p and -h are required and that you must add in your username password and database name.
