If you already have cooking experience from overseas, then you will need a skills assessment or recognition of prior learning to gain an Australian qualification. Normally, you need a Certificate III and 2 years' experience, or a Certificate IV in Commercial Cookery to be eligible for a work visa as a cook.
Are you already here in Australia? I would be happy to advise you about the occupations and courses available to qualify you as a cook here in Australia. Cooks and Chefs are in high demand right now, and it is expected to stay that way for a while yet!