For ripped Blu-ray disc games, the game data (often in ISO or JB folder format) should be placed in the games folder of your RPCS3 root directory. However, PSN titles installed via PKG are correctly installed to the \dev_hdd0\game\ directory.
Downloading copyrighted retail games that you do not own is illegal. The safest and most ethical way to obtain PS3 ROMs is to dump your own legally purchased physical Blu-ray discs using a compatible PC Blu-ray drive, or backup your own digital PSN purchases from your console. Ps3 Pkg Games Roms