the default database table prefix is ubbt_
Unless you changed it during the install.
You can look in phpmyadmin in your site control panel as well as see the full database name and users if your versions allow to see everything.
Otherwise go back to the main view of your site controlpanel and look for something like mysql. They are all a little different depending on what control panel your host provided but it would be where you created the database and user to begin with.
