The only place that I could find is :
Vehicle: 2008 Chrysler Town & Country Touring 3.8 V6 GAS
The cabin air filter should be replaced every 12,000 miles.
- Open the glove compartment door.
- Push inward on both sides of the glove compartment, then lower the glove compartment door.
- Carefully pivot the glove compartment downward.
- Through the glove compartment opening, disengage the cabin air filter access door retainers from the HVAC housing, then remove the cover,
- Through the access door opening, remove the filter element,
- Carefully install the new cabin air filter element into position
You were on the right track, it is behind the glove box.
Here are the instructions from the manual.
1. Remove the lower glove box bin from the instrument panel
2. Disengage the two retaining tabs (1) that secure the particulate air filter cover (2) to the passenger side of the HVAC air distribution housing (3) and remove the cover.
This is the cover behind the glove box that needs to be opened.
Just to update my answer. Your vehicle will have to be equipped with this optional filter. You wont find it if it is not one of your options. I now attached page 421 of the manual to verify my previous answer. Good Luck
Hope this helps