Click on this if you watch that 70's show!! I have a question about it...?

Ok, what is that episode where Jackie goes with Fez to return some of Donna and Erics wedding stuff and then they pretend to be engaged and they go to this party place and they see Kitty and red and Donna and Eric there.... Yeah. I know that it's somewhere in season 6/7 Im just not sure which episode... Thanks! =D