Well an ISO is usually an image of a CD or DVD, as far as I can remember, Akai never released 'expansions' on disc, and 'expansions' weren't really a thing until this generation of MPC's. CDXtract is also ancient, and hasn't been developed or updated in like a decade. You probably wont find much help with it unless you find someone that has been using it for quite awhile. If that ISO cant be directly read by Windows itself, then its probably an old Akai format sample cd, and you wont be doing much with that on a new MPC even if you managed to get them off of it and convert them to the new format.