''concat' is not recognized as an internal or external command,

I am following the Advanced CSS and Sass course by Jonas Schmedtmannon udemy , I am on the lecture(https://www.udemy.com/course/advanced-css-and-sass/learn/lecture/8274568#questions/9095858) where I try to do the build process using npm and I get this error:

Here is my JSON file:

I think concat was a command that came with npm?

The command I initially run is : npm run build:css

and here is some other data that results that I forgot to include in my first image:

natours@1.0.0 build:css C:\Users\noblegas\Desktop\Advanced_CSS_and_Sass_flexbox_Grid_and_animations\advanced-css-course-master\Natours\starter
npm-run-all compile:sass concat:css prefix:css compress:css

natours@1.0.0 compile:sass C:\Users\noblegas\Desktop\Advanced_CSS_and_Sass_flexbox_Grid_and_animations\advanced-css-course-master\Natours\starter
node-sass sass/main.scss css/style.comp.css

Rendering Complete, saving .css file…
Wrote CSS to C:\Users\noblegas\Desktop\Advanced_CSS_and_Sass_flexbox_Grid_and_animations\advanced-css-course-master\Natours\starter\css\style.comp.css

He is using an npm package call concat.

npm i -D concat

BTW, he installs it 4 minutes into “Setting up a Simple Build Process with NPM Scripts” in the “Natours Project — Advanced Responsive Design (Part 3)”.

Edit: I would also keep the Github repo handy and/or look at any source files you may have downloaded.