Not sure I understand how you could have the round mesh filter with no air box. The stock air filter for a Puch Maxi is a flat black plastic air box about 8" by 4" which sometimes has a round metal wire mesh filter that fits in the moped side of the air box. Sometimes there is also a flex tube that goes up into the round hole in the frame of the moped.
The other end of the air box attaches to the carb.
It won't run properly without this air box filter.