@PattiChati,
For old folks like me, "PRN" means "A printer which by default is connected to PC' parallel port named LPT1", and in old DOS days, one could print from an application by setting the printer to PRN.
Of course, all this implies your PRN file is plain text. If it has been formatted for a particular printer, you are out of luck.
What is the application this PRN file has been produced on?
Now, it seems that you HAVE a file with PRN extension, which you want to convert to PDF. If this is the case - open the file in recent Word version, and "Save As" PDF.
Or, install one of these damn PDF printers, open your PRN file on Notepad, and print it to that PDF.