Long-billed Corellas have a natural range in southeastern SA, western Vic and the Riverina area of southwestern NSW and have been significantly expanding their natural range in recent times. But with the help of humans there are also now feral/introduced populations in all Australian states (Perth, Alice Springs, Tasmania and along the NSW-QLD coast extending inland to Canberra-SH).
There is some debate to whether the population spreading to the NSW coast, southern highlands and Canberra is natural range expansion or introduced birds or both.
You might find the ALA Long-billed Corella page useful, which provides a map of their range. https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:9e3f5164-98ed-49bc-964b-cde4aeff6df6