Since you own this one, see if Dell has their Dell Documents on the machine or motherboard.
You usually don't need every connection. I start with the basics. Power, then the reset and after that it's all pretty much optional.
I have a Dell Precision T3500 and want to move the mother board to a full case. But the wires from the case to the mother board are not the same and not marked. I have no idea where the wire from the bigger case will go on the mother board. I do not know where to start. Any one have the diagram for these wire go from the new case on the mother board