Ah, ok, I figured it out. I've recently re-installed everything and hadn't made any sims yet, so the folder was not there. Which is why I got really confused about it all. So went into the game, made a random sim and saved to the bin. This caused the game to create the folder so I managed to copy and paste in my backup sims into the folder.
Now, for some reason i've placed a previously made lot into the downloads folder but it's not showing up. Is there something I'm missing?