AADConnect has a JSON file and the ability to export – and there are also various AADConnect documenters out there… but sometimes you just want to get a core piece of info without having to start the GUI of wade through many pages of JSON.
Get-ADSyncConnector | select Name
Note the name of your “internal” domain as the connector (the one that doesn’t have “AAD” at the end)
(Get-ADSyncConnector -name <ConnectorName>).Partitions.ConnectorPartitionScope.ContainerInclusionList
(Get-ADSyncConnector -name <ConnectorName>).Partitions.ConnectorPartitionScope.ContainerExclusionList