Your database folder is the folder where your database is stored in source control.
If your database is in a subfolder of your TeamCity build VCS root, select the Database folder is a subfolder of my build VCS root radio button, and then specify the subfolder path.
For example, if your VCS root is http://subversion.example.com/ and your database folder location is http://subversion.example.com/AdventureWorks, enter AdventureWorks.
In SQL Source Control, the location of the database in source control is displayed on the Setup tab, under Linked to. To copy the location, right-click on the path and then click Copy.
Note: the path you specify in TeamCity is relative to your build VCS root.