I don't think I was ever taught the "unit form" of something, but it basically just applies as follows: 111 = 1 Hundred, 1 Ten, 1 One. 725 = 7 Hundreds, 2 Tens, 5 Ones. etc.
So, $2 in Unit form would either be: 2 Ones. or 2 Dollars.
Hopefully that helps, have a great rest of your day! ^ ^ {-Ghostgate-}