how far is jiashan from hangzhou airport?I am flying out from srilanka,If I want to visit Jiashan,

Jiashan is closer to Shanghai than to Hangzhou City and Hangzhou Airport.
After you get at Pudong International Airport and then you can take the subway line 2 to Hongqiao Railway Station. In Shanghai Hongqiao Railway Station, you can take the bullet trains for Jiashan directly. The bullet trains will take you for about 20 minutes to arrive at Jiashan.
If you go to Jiashan from Hangzhou International Airport, you need to take the shuttle bus to Jiaxing and then take another bus to Jiaxian, which will be very complex for you to find and go.