How do you get different worlds on sims3?

Answer 1

Once you have done a certain amount of Scrolls and Tasks then the King will ask to speak with you personally, because you have been helping so many people and he will reward you with new Islands to go and explore.

Hope this helps. :)

Answer 2

you can download them from The Sims 3 website, or you can create your own with the create a world tool that is also available on the sims 3 website.