72 hour eligibility?

I am an Australian passport holder.
I am currently in Phuket, Thailand.
On June the 5th I fly direct to Shanghai and stay for 54 hours.
I want to leave the Airport as I have a Hotel booked in town.
On the 7th I fly to LA with a 2 hour layover in Tokyo.
Will I need to get a visa or will I be eligible for the free 72 hour pass? If I am eligible do I just tell the customs staff that checks my passport in Shanghai or is there another process.
Thanks greatly for your help