[PEX] Changing groups for different worlds?

Hey, i'v tried to using this method click here and the prefix doesn't even show! And it doesn't work for me. The only method I'v found that works for me is click here but only gamemode works. And I don't know how to make it so there inventory changes for every world they enter. This is what I want the world group changing to be on click me. I don't want to use the user method because I dont want to type it in for every player that joins my server. I want to link the member and all of the donor ranks to my "Factions" world. Please help! This is stopping me from continuing on my server!