public IEnumerable<Item> GetItems()

/// Get all the items that can be accessed from a folder connection. The items immediately 
/// contained by a folder, that is, the folder's children, are returned including folders
/// and individual items that can be used in ArcGIS Pro. This method does not return all 
/// items contained by any sub-folder that can be accessed from the folder connection.
FolderConnectionProjectItem folderConnection = Project.Current.GetItems<FolderConnectionProjectItem>()
                                                    .FirstOrDefault((folder => folder.Name.Equals("Data")));
await QueuedTask.Run(() =>
{
  IEnumerable<Item> folderContents = folderConnection.GetItems();
});

public async Task ObtainingGeodatabaseFromProjectItem()
{
  IEnumerable<GDBProjectItem> gdbProjectItems = Project.Current.GetItems<GDBProjectItem>();

  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    foreach (GDBProjectItem gdbProjectItem in gdbProjectItems)
    {
      using (Datastore datastore = gdbProjectItem.GetDatastore())
      {
        //Unsupported datastores (non File GDB and non Enterprise GDB) will be of type UnknownDatastore
        if (datastore is UnknownDatastore)
          continue;

        Geodatabase geodatabase = datastore as Geodatabase;
        // Use the geodatabase.
      }
    }
  });
}