You can see a list of Data Sources connected in your Account by navigating to the Data Manager from the lefthand navigation.
If you are an Agency, you can see all of the Data Sources connected in your Client Account by navigating to Clients from the lefthand navigation. The Data Sources column (marked with this icon: 
) shows Data Sources in Client Accounts. Hover over the i info icon to view a list of the specific Data Sources connected in the Client Account.
You can see the total number of Data Source Connections included in your subscription by navigating to Account > Billing and looking in the Usage section.