He's trying to have his conviction overturned -- and he apparently has legitimate reasons for this.
The people whose involvement in this case has now been reduced to a joke are the U.S. Justice Dept. lawyers who prosecuted the case. They have to go through a silly court proceeding to fight Arpaio's attempt to have his conviction overturned ... while knowing that Arpaio has been granted a pardon by their own boss anyway. They have to be thinking that this is a total waste of their time. Maybe they're considering a career doing something more respectable like running a meth lab or dealing heroin.
Or running guns to Mexican cartels.
Oh wait, they've already done that, haven't they?
why would he try to have his conviction over turned if he was pardoned?
He wasn’t convicted. He was found in contempt of court. No jury.