Hi, I'm Pete. Welcome to JustAnswer! I'm reviewing your question now, and will post back with your reply ASAP.
Peg, can you still log onto the account at https://www.amazon.com.au ?
If so, then the account is still working and you should be able to reregister the Kindle device to it.
If the account is no longer active with Amazon then you will need to contact Amazon to see if they can reactivate the account for you: