Shanghai free 144 hour exemption

I am an Australian citizen holding an Australian passport. I am going to be on a ship "Celebrity Millenium" which travels from Hong Kong on 8 April to Tokyo. It stops for 16 hours in the Baoshan port for Shanghai on 15 April and we thought we might need a visa, but the travel agent advises that an Australian citizen can spend 144 hours in Shanghai with a free exemption. Can you advise how I obtain this for my husband and myself.

With Kind regards
Beverley Downs