3 day free visa in Xian

You mean your trip is like Australia - Shanghai - XA - Hong Kong?
If so, you do not enjoy the visa free policy and you need to apply for a visa in advance.
The visa free policy is available for people who is making international transfering in China and the transferring time is within 72 hours.

Thanks for the reply but no I am not staying in Shangha. From Australia flight direct to Shanghai transfer at Shanghai International and on to XN

I think I know your meaning.
The transfer from Shanghai Pudong airport to XA airport is a domestic flight transfer, instead of a international transfer.
So you cannot enjoy the 72-hour free visa policy.

If your transfer in Australia - Shanghai - Hong Kong, you can enjoy the 72-hour free visa policy.

Hope this time, it helps ~