Hello, a similar question has been asked before here. The best answer is very long to copy all of it here, I'll just post the first 2 parts and you can look at the rest on the other post!
1st. Make sure your Downloads folder (which should be located in Users\(Current User Account)\Documents\EA Games\The Sims 2\Downloads.) has a capital "D". So it's Downloads. Spelled just like that.
2nd. Make sure you extracted the files correctly. Once you download them, don't just throw the file into the Downloads folder. You have to extract them using WinRAR or another kind of extracting program. (Download WinRAR here: https://www.rarlab.com/download.htm