If Australia was Pilot Paradise and it were that easy everyone would be doing it.
There are also many 250 hour pilots unemployed, under employed and under paid in Australia, however flying jobs are available for very determined applicants.
Read:
Conversion of overseas license.
Read:
Working Holiday Visa.
Conversion of a Working Holiday Visa to an Australian Permanent Residence Visa is certainly not guaranteed, particularly for pilots and may even be impossible. Your chances would be enhanced if you also held other vocational skills on the Skills in Demand List or had some entitlement to Australian residence.
You need to research your options very carefully, other wise it could be an expensive, futile experience and all end in tears.