Dont get frustrated, take time typing whatever you want to do (as so far I am myself getting confused in either you want to change the name of the database or you want to make changes within the database).
Rather, just type what you had done so far and what you want to do, as if I had unfortunately missed that part, then I can route you to good direction.
regarding replace command, like Emma mentioned (this may be confusing you), make sure you are logged into your Moodle as administrator, in your URL bar, just type this (assuming your moodle is running on this address http://localhost/moodle)
type
http://localhost/moodle/admin/tool/replace/index.php
that is about it, hit enter and you'll have Moodle's replace utility available before your eyes.
This should not confuse you, or should it?