Thanks for your question.
Please pay attention that Australia citizen still need Visa to enter Vietnam.
In this case you are required Visa for 14 hours transit in Vietnam. Please apply for Visa on arrival here https://www.vietnam-evisa.org/apply-visa.html. Just fill your information in the application form then you will receive the Visa approval letter via your email. Then you print it out and use it to get Visa stamp at the Vietnam airport upon arrival
The fee for 1 month single Visa is 19USD/person