SASS dependency not found in Laravel and Vue.js project

I inherited a Laravel project that uses Vue.js as the front end. However, I can't seem to get things to work.

Here are the commands I executed:

john@mail:~/$ cd ~/html/app
john@mail:~/html/app$ composer install
john@mail:~/html/app$ php artisan migrate ---> at this point the website is viewable, so i guess all the npm resources were already compiled with the project
john@mail:~/html/app$ npm install
john@mail:~/html/app$ npm run watch

But the last command yielded the results below.

@ watch /var/www/html/app cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --watch --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js

10% building modules 1/1 modules 0 active Webpack is watching the files… 95% emitting ERROR Failed to compile with 14 errors
7:16:18 PM

This dependency was not found:

• /var/www/html/app/resources/assets/sass/app.scss in multi ./resources/assets/js/app.js ./resources/assets/sass/app.scss

To install it, you can run: npm install --save /var/www/html/app/resources/assets/sass/app.scss

package.json

{
    "private": true,
    "scripts": {
        "dev": "npm run development",
        "development": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
        "watch": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --watch --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
        "watch-poll": "npm run watch -- --watch-poll",
        "hot": "cross-env NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
        "prod": "npm run production",
        "production": "cross-env NODE_ENV=production node_modules/webpack/bin/webpack.js --no-progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
    },
    "devDependencies": {
        "axios": "^0.17",
        "bootstrap-sass": "^3.3.7",
        "cross-env": "^5.1.3",
        "jquery": "^3.2",
        "laravel-mix": "^1.0",
        "lodash": "^4.17.4",
        "node-sass": "^6.0.1",
        "sass": "^1.35.1",
        "sass-loader": "^12.1.0",
        "vue": "^2.5.7"
    },
    "dependencies": {
        "foundation": "^4.2.1-1",
        "jquery-ui": "^1.12.1",
        "lang.js": "^1.1.14",
        "slick-carousel": "^1.8.1"
    }
}

Any ideas how I can resolve this issue? To me, the instruction to npm install --save /var/www/html/app/resources/assets/sass/app.scss doesn't seem right.