Since you didn't mention whether you checked TheSims3.com:
The Sims 3 Store may not display a world as owned when you view the world's page. You must go to My Page (your TS3 profile page) on TheSims3.com and check whether the world icon is grayed.
Check your profile page on TheSims3.com to see if the worlds you have purchased seem as owned. They are at the bottom of the left sidebar.
If a world's icon is not grayed, that means you own that world. You can download it from your purchase history or from the downloads dashboard in the game.
There is a purchase history page on TheSims3.com. You will find all purchased Store content there, including free content (e.g., Riverview) and bonus content (e.g., limited edition content).
Alternative to this purchase history, you can use the downloads dashboard in the main menu after logging in to your TheSims3.com account in-game. This window will also show all owned content, including purchased worlds.
Also, just in case, make sure your TheSims3.com ID is the one linked to your EA account in which you purchased the worlds. You can check this from your EA account information page. See Game Personas at the bottom of the page.