Database info changed

I know this is out there somewhere. It happened before and I found it but I cannot find it anywhere and I need my website to have as little downtime as possible. Basically my database info was changed and now xenforo cannot get to it so it says "An unexpected database error occurred. Please try again later." I know there is a file I can upload via FTP to repair/reconfigure this. Can someone please point me to this?

Thank you