Welcome to the group, AlvinJames. As said, the cabin air filter is the first place to look.
Audi and VW seem a bit more prone to smells, based on owner’s comments. It’s similar to home window AC units. “Mildew” can collect on the evaporator. Less common, the drain tube will plug (water gathers). If the smell doesn’t go away with the filter change, this owner posted a tutorial about cleaning the system, at filter changes.
https://www.audiworld.com/forums/q5-sq5-mki-8r-discussion-129/smelly-air-conditioner-remedy-2908720/