If any program is capable of converting .ppj files to .prproj, it would be Adobe Premiere Pro from which both of these projects originate. Maybe a simple re-save is enough, but it may be that this conversion is actually not possible or useful.
It looks like this conversion is actually importing older Premiere projects to newer version and saving them again in latest format. Some users have partial success when others had none, so it seems that this conversion can be difficult for some users. Your best bet would be to to contact Adobe support or consult their forums about this subject.