Hi Michele and welcome to the forums.
It doesn't appear that you are hosted with TCH so not sure what help we can offer.
On a TCH Server you create a database the name becomes cpaneluser_database-name same with the user for the DB. The cpaneluser_ is pre-pended to the user name.
Not sure if your hosting provider has defined it that way or not but maybe their support can point you in the right direction.
Also, if you are trying to connect to the database from a different account, you need to use the domain name, not just localhost.