This is an I/O panel from a Micron computer.  …same case as the Dell.  It had the USB holes in it already.   I cut the COM2 hole.  You can see that the little backing panel already has the proper holes in it.   I put tape over the sound card holes for mobos without onboard sound so I don’t mess with the airflow from the front to the rear of the case.  This I/O panel has clear packing tape over the sound card holes.