are there bus from rudong to yiwu? if so how many hrs and what time?

There is no direct bus.
You can take a bus from Rudong Bus Station to Nantong East Bus Station (CNY18, about 70 mins). And then in Nantong East Bus Station, you can take a bus to Yiwu. The bus leaves at 15:00, and the fare is CNY149, the duration is about 4 – 5 hours.