need to know where to replace filter for cabin air.
Autozone.com offers free online repair manuals/info. You have to set up an account to access your vehicle repair guides. Not sure if they have air filter info or not, but doesn’t hurt to look.
You can also look for an online forum like this one, but specific to your make of vehicle.
Or you can look in the owner’s manual. If yours is missing, perhaps you should find one of those - tho a repair manual is never a bad thing to have access to.
Things obviously vary, but the most likely location/access is going to be in the area of the glove box - behind or down underneath.
I don’t know what year your caravan is, these instruction below are for a 2001
Cabin Air Filter
Removal & Installation
Locate the air filter door on the bottom of the lower front HVAC housing just on the right of the center.
Slide the air filter door latch toward the rear until it engages the opened stop on the door.
Pull the air filter door straight down to disengage it from the air filter opening of the HVAC housing.
Reach through the air filter opening and grasp the filter with your fingers.
Pull the air filter straight down and out.
NOTE: Make sure to install the filter with the word “Airflow” and an arrow pointing toward the center of the vehicle. The filter will clog prematurely if not installed correctly.
Install the filter fully into the HVAC housing. Make sure to install the filter with the word “Airflow” and an arrow pointing toward the center of the vehicle.
With the latch still positioned against its opened stop, install the air filter door on the HVAC housing air filter opening.
Slide the air filter door latch toward the front until it contacts the closed stop on the door.
Check with aftermarket filter manufacturers. Check the local public library.