npm run dev missing script error

[YasBenAll]

I've never used node.js and npm before so I'm stumbling across some newbie mistakes. One error I get is that when I try to run npm run dev, Git bash returns the following error code:
npm ERR! missing script: dev

0 info it worked if it ends with ok
1 verbose cli [ 'C:\Program Files\nodejs\node.exe',
1 verbose cli 'C:\Program Files\nodejs\node_modules\npm\bin\npm-cli.js',
1 verbose cli 'run',
1 verbose cli 'dev' ]
2 info using npm@6.4.1
3 info using node@v10.15.3
4 verbose stack Error: missing script: dev
4 verbose stack at run (C:\Program Files\nodejs\node_modules\npm\lib\run-script.js:155:19)
4 verbose stack at C:\Program Files\nodejs\node_modules\npm\lib\run-script.js:63:5
4 verbose stack at C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:115:5
4 verbose stack at C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:418:5
4 verbose stack at checkBinReferences_ (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:373:45)
4 verbose stack at final (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:416:3)
4 verbose stack at then (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:160:5)
4 verbose stack at ReadFileContext. (C:\Program Files\nodejs\node_modules\npm\node_modules\read-package-json\read-json.js:332:20)
4 verbose stack at ReadFileContext.callback (C:\Program Files\nodejs\node_modules\npm\node_modules\graceful-fs\graceful-fs.js:78:16)
4 verbose stack at FSReqWrap.readFileAfterOpen [as oncomplete] (fs.js:237:13)
5 verbose cwd C:\Users\Yassi\TEST
6 verbose Windows_NT 10.0.17134

I don't know what I should be adding to my package.json file to make this work. Could anyone help me with this please?