i arrive at pudong airport on Jan 7th. the next morning i need to get to Kunshan railway station

Well, you can take Shuttel Bus Line 5 to Shanghai Railway Station, and then catch a train to Kunshan. It takes about 40 minutes and CNY11.

Or you can take an intercity bus from the airport to Kunshan first, which is available from 9:00 to 20:45 with an interval of about 1h. It takes 2h and CNY76.
After getting there, you can take a taxi to the railway station within 15 minutes.