I found a new way of searching Trove which others may already know about but it was new to me so I thought I would share it. Hope it helps someone!
Searching All Newspapers In A State
Go to Trove website: www.trove.nla.gov.au
Click on “Digitised Newspapers and more”.
On the map of Australia click the state you want to search. In my case it is South Australia.
Click in the box “Limit to South Australian titles”.
Click in the search box, type in your search and press enter.
Your search will show only results for South Australian newspapers. This can be repeated for all Australian states.