2000 Dodge Intrepid Air Cabin Filter

I was first wondering if this vehicle has a Air Cabin Filter and second where is it located? My problem is whenever the heat or Air is turned on in the car there is a distinct smelly smell of must or mildewness. Almost like the smell of an old shoe. We have had the car since it's birth but within the past few years it has had this smell and we have tried everything from deodorize spray to cleaning the seats and carpets. The thing is it is not a dirty car and has been well taking care of and is a daily driver back and forth to work. We are left only thinking maybe the air cabin filter needs to be changed if there is one?