Jim was a mechanic who held the DeLorean and the Magic School Bus at his auto shop in Stale Pancakes 7. Unintentionally, Jim had a key role to play in the transformation of Willy Sketch into Doc Brown. In his adventure with Sherlock and Willy through time, he became friends with himself from the past, and the two began a law firm.
Unless they escaped to the future or past at the time of "Clone 732", it's probably the case that the Jims were either killed or brainwashed as is detailed in the intro of "BATTLE!".