How to install PLayMemoroesonline App on Mac mini?

Sony no longer supported Play Memories.

https://support.d-imaging.sony.co.jp/www/disoft/int/download/playmemories-home/mac/en/

If it doesn't install or work as expected on a new Mac, then you will need to contact Sony or use something else.

Personally I have used iPhotos, now Photos for many many years. It is more than capable of managing, handling and editing photos from every camera that I've ever connected to any Mac. macOS - Photos - Apple