Well, at Shanghai Pudong Airport(https://www.travelchinaguide.com/cityguides/shanghai/pudong-airport.htm), there are two buses departing to Yiwu directly at 11:10 and 17:10.

If you miss the bus, you have to make transfer in downtown area. After arrive at Pudong, you should take shuttle bus Line 7 to Shanghai South Railway Station, where you could take a train to Yiwu. Or, walk to the bus station located to the south square of the train station, you could take a bus to Yiwu as well.