You should get to SHanghai South Railway Station to catch the train. For the time is late, you should miss the airport bus to the railway Station. You can take Line 2 to Jing'an Temple (or the night line to the city center and get off at the nearer stop to the railway station), then change to taxi there. K71 departs in the afternoon, you can consider to have a rest at the airport and go to the railway station in the morning by airport Line 7.