"I cannot run Stat/Transfer on Debian Linux 9.4. It says I am missing libpng12. What shold I do?"

libpng12 is not present on Debian 9.4 (Stretch). You can download it from Jessie repository:
https://packages.debian.org/search?keywords=libpng12-0

To install it, run the following command:  

"sudo apt install ./libpng12-0_1.2.50-2+deb8u3_amd64.deb"

and run the Stat/Transfer GUI.

Stat/Transfer may report on the missing library libcanberra-gtk-modue (it will depend whether or not the library has been installed during OS installation).   You can install this from Stretch  repository or Stretch DVD (it is a  standard Debian 9.4 library).