$ sudo apt-get update
$ sudo apt-get install nautilus-script-audio-convert 

nautilus-script-audio-convert is installed in your system.

Make ensure the nautilus-script-audio-convert package were installed using the commands given below,

$ sudo dpkg-query -l | grep nautilus-script-audio-convert *

You will get with nautilus-script-audio-convert package name, version, architecture and description in a table

nautilus-script-audio-convert package basic information: