You cannot put .Sim3Pack files into the Furniture CC Folder. That file type belongs in Downloads and must be installed via the Launcher. The launcher is terrible for furniture.

Specializes in "4t3" conversions, bringing modern Sims 4 furniture into The Sims 3.

(Sims 4 to Sims 3), providing modern, detailed furniture and clutter that looks stunning in-game. Onyxium (TSR)

Finding the perfect furniture folder for The Sims 3 often involves looking for "CC sets" or "merges" that group items by aesthetic. Popular creators frequently offer large collections of high-quality, Maxis Match or realistic furniture. Recommended Sims 3 Furniture Creators

Custom content for The Sims 3 is stored in two primary locations depending on the file type. The main user directory is located at .

This is the high-traffic area. Here lies the heavy lifting: sofas, dining tables, beds, and desks.