Pack Selection

Hello! I want to preface this by saying I'm not a tech person, I barely understand modding games or figuring out glitches. So, if you happen to figure something out, you'll need to explain it like I'm five years old. 

Now, I can't find the Pack Selection thing in my Sims game, I did have it once but that was a few years ago. I've tried to redownload everything, remove my mods, clear the cache and the thumbcache, and I still can't find it. Can someone help?