I wanted to download the paternity clothes and the creator said to delete 4 cache files.... but I counted 6 files with the word cache in them. I've never deleted game files before and am scared to do it. Can anyone please tell me specifically which ones are safe to delete?

Here's what I have:

DC cache
World caches
CAS part cache (this one has the monkey icon)
Compositor cache (again with the monkey)
Script cache (monkey)
sim compositor cache (monkey)

Also, do I delete the file itself, or just the contents in the file? Does this wipe out stored data/sims/downloads?

First I think we need to get some terminology together:
File.. a single file
Folder..a folder that contains files. Normally yellow and looks..like a folder!
There is a difference and you need to understand those differences so you don't go deleting folders.

OK. You can delete the contents of the World Caches folder(although it's probably not necessary), AND these 'files'-
* CASPartCache.package
* compositorCache.package
* scriptCache.package
* simCompositorCache.package

If you have anymore questions, let us know.