The only real answer to that I should think is to contact an approved Pt147 organisation and get them to assess you under Recognition of Prior Learning. They will then advise you on what modules you will need to do for Cert IV (AME) or Diploma (LAME).
Aviation Australia in Brisbane is probably the biggest operator in this, but there are couple of TAFEs that do this such as Padstow in Sydney. Maybe a couple of other places...there used to be one in Nowra as well??? Expect to pay around $2k!!!! Welcome to the world of aircraft engineering qualifications!