Convert PRN to DOC

We do not know about any utility or converter that can be used to for the purpose of prn to doc conversion, which is something like export of .prn documents (perhaps from old Lotus 1-2-3) to MS Word format. At best you can try to manually copy and paste if that's even possible for your .prn files, but that will work only if the .prn file is not binary. You can always try to open your .prn files manually in a text editor / word processor and see if some text can be at least partially recovered.

Simply put, it is impossible to convert PRN to DOC directly.
Thus, there is no so-called prn to doc converter or a free online .prn to .doc converter to be found.