No, there is no public, one-click software tool that can automatically convert a standard PS3 PKG file into a working, native PS4 PKG file.
The "exclusive PS3 to PS4 PKG converter" is a myth designed to exploit eager gamers. Stick to official streaming options or PC emulation via RPCS3 to enjoy your favorite seventh-generation classics safely.
Buy a physical PS3 console to play original discs natively without compatibility glitches.