The dealer group I work for was sold to another dealergroup, and now the new group is not paying me

My car dealership was recently sold from one owner to another. The new owner has not paid my commissions, and while I have not yet spoken to my gm, I think he will refuse to pay and will do so because neither of us has a copy of my old payment plan (I lost mine and the old dealer group has it but has not found it yet, and obviously I have not signed a new payment plan yet)

Can they refuse to pay my commissions (I am salary plus commissions) without a copy of the old payplan? Or can I bring in prior records paystubs and bank statement that show a history of commissions paid in the past?

Also, I live in illinois, but work in iowa. The old dealer group maintains operations in illinois, and wisconsin (mine was the only dealership they had in iowa before selling) the new dealership group owns and operates exclusively in iowa