Welcome to the Bunnings Workshop community @Lee49. It's wonderful that you've joined us, and many thanks for your question about working out the required tiles for your floor.
After you have worked out your floor square meterage, determine the square meterage of the tile by multiplying its length by width. You can then divide your floors area by the tiles area. This will give the number of tiles you'll need. For example, there are 1000 square centimetres in a metre squared, and there are 90 square centimetres in a 30cm x 30cm tile. If you divide 1000 by 90, you'll see you need 9 tiles per square metre. It's always best to pick up a few extra for wastage and cutting.
If you'd like to tell me the floors area and what size tile you're using, I can work it out for you.