Thanks for posting those screenshots. From the error message, it looks like C:\Users\Demo\Desktop\soundmodem.exe is not the path to the soundmodem application. You can take a look at the path setting in the APRS application, or use the search feature in the file manager or perhaps the Start program to find where soundmodem.exe is located in the file system.
Does that make sense? You are very close to success!
73 Constrainted