P3X-447
From The Stargate Omnipedia
Planet in the Pegasus Galaxy that a rogue Aiden Ford was monitoring while a Wraith hive ship had landed there. Intent on gathering more Wraith enzyme, he witnessed a commander separate from the ship and go through the planet's Stargate. He pursued and wound up on P3M-736.
This planet's designation may be inaccurate, as Ford was not certain that he had it straight.
KEY EPISODE
Runner - Back with McKay, Ford explains that he traveled from P3X-447, probably, to P3M-736.