@WarrenBelz
After try and try again , finally I found answer......
in combobox formula :
Sort(getsubordinate,Result,Ascending)

in dtat table formula :
Filter(APP1, Value(Left(Title,8))>=Value(Text(Department_manager_query_start_date.SelectedDate,"[$-en-US]yyyymmdd"))&&Value(Left(Title,8))<=Value(Text(Department_manager_query_end_date.SelectedDate,"[$-en-US]yyyymmdd")) && user_email in Department_manager_query_subordinate.SelectedItems )

After this , I choose more than one person , the person's info will show in data table ~~~~
YES , I complete it !!!