|Well first you identify the motherboard.|
Then you go to the manufacturer's website and download the motherboard manual.
Then you read the manual which will tell you exactly where the header is for the front connectors and which is which.
Here is one clue though. It makes no difference which way you connect the power switch wires since that switch is a Momentary Contact switch. The two LED headers must have the correct wires since the LEDs will not light up if the wires are switched.
Goin' Fishin' (Some day)