It's impossible to say if the Simple Viewer is compatible with Windows 10 or not since there is no way to download it. Panasonic does not offer the possibility to download their products. Simple Viewer is bundled with the CD that arrives with the Panasonic product. If you lose it, then there is no way to download it.
However, if you have the CD, right click the Simple Viewer application and go to Properties > Compatibility. Choose Windows XP Service Pack 2 from the list and then run it. It's the best way to tell if it works on Windows 10 or not.