Help Installing Certain Exspansions

Ok so I am no computer wiz... But I really need help. I got an official copy of the sims 3 and a official copy of the sims 3 pets. However I want the ambitions expansion pack, is there a guide to that? Because when I try to install it, the thing tells me that I dont have the Sims 3 installed when I do.

Darn... Its from steam :l Is there seriously no way to get a crack? Because that kinda makes me sad... Unless I download a different copy of the game from here.

Thanks for the advice :DI will infact download it from here, is there any way to transfer the save files? Also I have free item packs from the sims website that you guys dont happen to offer (ford and prius packs) I originally tried getting them from here and they didnt work, is there a way to move that?

The folder with all that information (saves, mods, other game info) should still be located at "Documents\Electronic Arts\Sims 3" so check if it's there. If so, then before installing the new game, just make sure to back that up and uninstall the steam version. If not, I'm sure we can find where Steam decided to hide those files at.