Error Connecting Database?

I had some malware and, long story, somehow in the re-installation process my database can now no longer connect to the WP installation. I have several databases because I have several subdomains, but I am sure I know which one it is. However, I don’t know how to retrieve the DB password so that I can edit it into the wp-config file. Also, does it matter what USERNAME I have in the wp-confg, as long as I have the same user name able to access the database my my cPanel. My host is bluehost, btw.