The Ports/8em module is for use with the Acceleport Xem host adapter:
The external Ports modules actually draw power from the Host Adapter card, so as long as only 1 or 2 Ports modules are daisy-chained off the card, no auxillary power supply is necessary.
If additional modules (up to 4 total for the card) are daisy-chained off the first two modules, auxillary power is then required. The part number for the power supply, should one be needed in your case, can be found at the preceeding link under the "View Related Accessories" link.
Also, here's a link to the product page where the hardware manual can be found: