I lost my australian passport, what do I do?

I lost my passport sometime last week. It fell out of my bag. I have been using it for ID but it expired years ago. I have not used the passport for travel in over 10 years. Just ID. I am an Australian in Australia. I want to start traveling and I am unsure how to report it. I don't know the passport number or expiry date or any of the official details. Do I just report it and give my name? I don't know..