If you would like go to Shanghai by bus, you should take a coach at Hangzhou Passenger Transport Central Station, not the east bus station. All of the bus lines operted by the East Bus Station have been transferred to the Central Station. You could take the bus K508 from the railway station to get to the bus station directly. Well, please refer to the info on this page: https://www.travelchinaguide.com/cityguides/zhejiang/hangzhou/getting-there.htm