I need to find my father malcolm george chapman?

he was born the 19th april 1963 which makes him about 46 last known living in goldcoast qld but has regularly living in adelaide. his mother is pat and father is george. he lived in gympie, qld where he married my mother and i lost contact with him 6 years ago. desperatly tryingt o find him for medical history and for him to know his eldest daughter is married and he has 3yr old grandsons. i am dying to have my daddy back i miss him terribly, he is always in my head. PLEASE HELP ME!!!