Size filter for mr furnice carrier weathermaker 8000TS

Size filter for my furnice carrier weathermaker 8000TS

FurnAce filters come in all sizes and may not even be in the furnace. If there is no slot where a filter should go, check the cold air returns. I worked on a condo last week and it had a 20X20" filter in a large wall return. Filters are usually on the air return side but some brands have them on the supply side just above the lower air handler door.