user file that you can give to your game group so that everyone will then have the Archmage PrC available to them in HL.
If you want to convert the Archmage PrC to Pathfinder for your group as a house rule then the Editor built into HL is what you want to look at. So if converting from 3.5 you would replace the PrC levels with Wizard and simply take the appropriate feats. The class was broken down into Feats instead.
In the Pathfinder RULES there is no longer an Archmage PrC class. Your mixing the Pathfinder Adventure Paths, which is Golarion Fluff, written in 3.5 D&D rules with the Pathfinder CORE rules. Though that may be, they are also Pathfinder - Golarion books and accordingly are still entirely valid when playing a Pathfinder game, which means the Archmage class is still in effect as far as the Pathfinder gaming group is concernded.
