How to fix missing script : serve?

When I run npm run serve in terminal, I got error "missing script : serve" and here my package.json file :

{

  "name": "internship",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "serve": "vue-cli-service serve",
    "build": "vue-cli-service build"
  },

  "dependencies": {
    "core-js": "^3.6.5",
    "vue": "^2.6.11"
  },

  "devDependencies": {
    "@vue/cli-plugin-babel": "~4.4.0",
    "@vue/cli-service": "~4.4.0",
    "node-sass": "^4.12.0",
    "sass-loader": "^8.0.2",
    "vue-template-compiler": "^2.6.11"
  },

  "browserslist": [
    "> 1%",
    "last 2 versions",
    "not dead"
  ]
}