Welcome to the forum.
Unfortunately, the PREL files are not X-platform.
The best that I can think of, would be to output a MOV/MP4 file from the PC version, for Import and additional editing on the Mac.
I would second Hunt's suggestion about exporting your Premiere Elements 9.0/9.0.1 Timeline Windows to a .mov or .mp4 file for import into the appropriate preset in Premiere Elements 12 Mac.
On the Windows side just verify project settings for the Timeline as well as the export setting under the Advance Button of the preset that you select under Share/Computer/QuickTime (.mov) or Share/Mobile Phones and Players (.mp4).
Please update us on your progress.
Thanks for the tip. I have been able to save to a QuickTime (mov). Got lots to move but this is working. Thanks again, Ed