Where is the location of the filter of my central aircon section?
Answers: In the return air duct... depends on the element you have... could be at the stub of the furnace if you have an up-flow system. Or maybe the ceiling return air grill for an attic mounted component. Need more info to properly answer.
Papa is right.
The filters are considered cog of the ducting system NOT the cooling system so it can differ in different houses. But repeatedly they put them right before the blower or surrounded by the return air vent.
You simply have to find it.