The only .pfp files we know about, are projects from a software called Panorama Factory. This means that if any kind of png to pfp conversion is possible, it would be more of import of PNG files to new or existing projects in the tool. It is a graphics/photo editor so it does make sense this way.
Of course it might very well be a typo and you were not searching for .pfp files but something else.
Updated: October 23, 2023