Air conditioners come in two by two by many models.. but for this post only one of the "2s" is important,,,, Ducted, and not ducted.
ALL not ducted fit in a 14" square hole.. that is the "Foot print" a 14" square hole. They are ALL the same, a 14" square hole.
Ducted ones the ducting unit may be different. So there you need to be careful, but non ducted, and i suspect that is what you have, all fit the same 14" square hole.. By the way so do Ducted units, but again the ducting unit fits INSIDE the hole, then there is a top part, and a bottom part.