There have been several sites over the years that have provided PS3 PKG files. However, due to the changing nature of these sites and the legal issues surrounding them, I won't list specific sites. Instead, I recommend searching for the latest information and reviews on gaming forums or tech websites to find safe and legal sources.
Instead of moving files via USB, you can serve them from your PC directly to the PS3. Ps3 Pkg Site
A PKG file is an installation package format used officially by Sony for distributing PlayStation Store content, system updates, and game patches. On a standard, unmodified PS3, these files are encrypted and signed to prevent unauthorized installation. However, on a PS3 running or HEN (Homebrew Enabler) , users can install unofficial, decrypted, or signed PKG files to expand the console’s functionality beyond its original limitations. There have been several sites over the years
Only download from reputable community forums to avoid bricking your console or catching a virus. Instead of moving files via USB, you can