CC listed as 'mod conflict' with game

Hello! so two weeks ago I was playing sims 4 and so I decided I wanted to do a few cc shopping so I exit out the game.  I accidentally downloaded some sims 3 content and it ended up in my sims 4 folder and so I had to use the mod conflict detector to find out what was wrong with my game and why wasn't it launching, since then I started a new mods folder with everything that was in my old folder and I got a message saying the game won't start up which is weird because its the same cc I've been using for months. Most of my cc is updated or some don't need to be updated but It still shows up in the Mod Conflict Detector as a 'mod conflict' and now I'm really confused because I don't know what to do.