I am trying to install npm package dependencies in to my angular application and i am getting this error. Any help to fix this?

npm ERR! code E404
npm ERR! 404 Not Found: error-ex@^1.2.0
npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\Dilushi\AppData\Roaming\npm-cache\_logs\2020-02-12T13_07_17_602Z-debug.log

I will attach my package.json file here.

{
  "name": "app-pfe",
  "version": "0.0.1",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^6.0.2",
    "@angular/common": "^6.0.2",
    "@angular/compiler": "^6.0.2",
    "@angular/core": "^6.0.2",
    "@angular/forms": "^6.0.2",
    "@angular/http": "^6.0.2",
    "@angular/platform-browser": "^6.0.2",
    "@angular/platform-browser-dynamic": "^6.0.2",
    "@angular/router": "^6.0.2",
    "@ng-dynamic-forms/core": "^6.0.6",
    "@ng-select/ng-select": "^2.18.0",
    "angular-webstorage-service": "^1.0.2",
    "angular2-moment": "^1.9.0",
    "core-js": "^2.5.4",
    "inspector": "^0.5.0",
    "jsrsasign": "^8.0.12",
    "ngx-auth": "^5.0.0",
    "ngx-bootstrap": "^5.0.0",
    "node-sass": "^4.11.0",
    "rxjs": "6.3.3",
    "rxjs-compat": "6.3.3",
    "underscore": "^1.9.1",
    "zone.js": "^0.8.26"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "^0.13.8",
    "@angular-devkit/build-ng-packagr": "~0.6.8",
    "@angular/cli": "~6.0.2",
    "@angular/compiler-cli": "^7.2.14",
    "@angular/language-service": "^6.0.2",
    "@types/jasmine": "~2.8.6",
    "@types/jasminewd2": "~2.0.3",
    "@types/node": "~8.9.4",
    "codelyzer": "~4.2.1",
    "jasmine-core": "~2.99.1",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "^4.0.1",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "~1.4.2",
    "karma-jasmine": "~1.1.1",
    "karma-jasmine-html-reporter": "^0.2.2",
    "ng-packagr": "^5.1.0",
    "protractor": "^5.4.1",
    "ts-node": "~5.0.1",
    "tsickle": ">=0.25.5",
    "tslib": "^1.7.1",
    "tslint": "~5.9.1",
    "typescript": "3.1.1"
  }
}