domain transfers and sub doamins confused

[kingy123]

1) i have a domain www.skplastering.biz and i want it to be www.skplastering.com.au, and dont no what webstite to make the domain name on because u dont do .com.au can u help with that.

2) all my pages will be www.skplastering.biz/rendering e.g
i want it to be www.skplastering.com.au/rendering. would i be able to do that and how.