The newer Unos (rev 3) have four extra pins. You don't need to use those. The shield should still plug in, omitting four pins (basically two on one side and two on the other, nearest to the USB socket).
The newer Unos (rev 3) have four extra pins. You don't need to use those. The shield should still plug in, omitting four pins (basically two on one side and two on the other, nearest to the USB socket).