There are four pairs of wires in an Ethernet cable, and an Ethernet connector (8P8C) has eight pin slots. Each pin is identified by a number, starting from left to right, with the clip facing away ...

The only catch is that for the Type 3 and 4 PoE standards that represent the current state of the art, you need 8-pin Ethernet cable. Some older networks still use 4-pin, so check before proceeding.