Cabin filter replacement

Hello,

Anytime you have musty smell, changing the cabin filter it a good first step.
You also want to spray some Ozium through the cowl under the windshield.
As the smell is due to bacteria forming, typically being wet or in high humid area. Ozium is a anti bacterial spray and can be purchased at any of your local auto parts store along with many big box retailers. That spray will get rid of most of the bacteria and should improve the smell.

Also this vehicle did not have factory cabin air filter, it was a dealer installed option and not all vehicle got that option.
It was installed on the passenger side cowl bottom of the windshield.

https://www.youtube.com/c/2carpros/featured

I have attached the diagrams for your reference.

Please let me know of any questions.
Thank you.