cabin air filter location

Here you go-

GLOVE BOX REMOVAL
Open glove box.
Push in on sides of glove box bin and lower door.
Remove glove box dampener retaining clip from bin key hole by sliding retaining clip rearward. See Fig. 1
Fig. 1: Glove Box Dampener
Courtesy of CHRYSLER LLC
Pivot glove box downward and disengage hinge hooks from instrument panel.
Remove glove box.
PARTICULATE AIR FILTER REMOVAL
Disengage the two retaining tabs (1) that secure the particulate air filter cover (2) to the passenger side of the HVAC housing (3) and remove the cover. See Fig. 2
Fig. 2: Removing/Installing Particulate Filter Cover
Courtesy of CHRYSLER LLC
Remove the particulate air filter (1) from the HVAC housing (2) by pulling the filter element straight out of the housing. See Fig. 3
Fig. 3: Removing Particulate Filter

my sebring was the previous year (2006) and it doesnt have a cabin air filter. is it possible to upgrade my current motor unit shown with the type shown above in order to have a cabin air filter?

If the car is not designed with it you cannot include one unless you change the entire heater box which is very expensive.