You mean this one? https://forum.audacityteam.org/t/change-speed-stretch-audio-to-a-specified-length/23332/1
If you open the .ny file in your text editor, you will see that most of the code is just handling the input and checking for stupid user errors 
It’s only when you get to the final line that it actually does something. Does this look familiar:
(force-srate new-srate s)