Yes — these .PDN files appear to be Polaroid’s old camera format, and the practical solution is to use the original Polaroid software to convert them, typically to TIFF.

From the community answers:

• The correct software is Polaroid “PDC Studio” for the PDC-3000.
• A working copy has been reported on the Internet Archive.
• It can convert image files from a folder on your computer, so you may not need the camera connected once the files are copied.
• The PDC-2000 drivers/software do not reliably work with the PDC-3000.
• Because the software is very old, you may need an older Windows environment such as Windows 98, or possibly Windows XP compatibility/virtual machine support.

So the best path is:

1. Find the archived PDC Studio software.
2. Run it on an older Windows install or VM if needed.
3. Use it to export/convert the .PDN files to TIFF.

There does not seem to be a widely supported modern reader for this format, so original software in a legacy OS is likely your best option.