This file is already .prc in my "Samples" folder "GolfScoreTracker.prc". In "Documentation" folder there is some info to those tools, all I know about those tools:
"jartoprc.exe" - converts .jar(or .jad+.jar) to .prc, 'jartoprc.exe -jar:midlet.jar', for more info "jartoprc.exe -help";
"jartoprc_w.exe" - is windows gui for "jartoprc.exe".
Download a MIDlet from this
website, try converting it to .prc, worked for me.