Backup and restore help

[.m.]

MyBB's Stock theme is named as Default & its templates set is named Default Templates.

other themes & template sets are named similarly.
eg. Netpen theme & Netpen templates

at Themes section of forum admin panel,
you can delete a theme by using options button which appears next to theme name

similarly a templates set can be deleted if the set is not used by a theme.

after deleting unnecessary themes & template sets, you can take
database backup & files backup to use at another web host server