Where can I find my downloaded cars in The Sims 3?

I opened already the The Sims 3 Launcher, checked and installed some of the vehicles, and it said that it installed successfully. I opened the game, went into the cars' section, and I found only the cars that are already built-in in The Sims 3. I checked my The Sims 3 Launcher and I do run the game with custom content.