AngularFireのモジュールがnot foundになる

Question

#環境
Ionic + Angularでアプリ開発をしています。

環境は以下の通りとなります。
ionic info

Ionic:

   Ionic CLI                     : 6.9.2 (/usr/local/lib/node_modules/@ionic/cli)
   Ionic Framework               : @ionic/angular 5.1.1
   @angular-devkit/build-angular : 0.901.7
   @angular-devkit/schematics    : 9.1.6
   @angular/cli                  : 9.1.7
   @ionic/angular-toolkit        : 2.2.0

Capacitor:

   Capacitor CLI   : 2.1.0
   @capacitor/core : 2.1.0

Utility:

   cordova-res (update available: 0.14.0) : 0.6.0
   native-run (update available: 1.0.0)   : 0.2.8

System:

   NodeJS : v10.15.1 (/usr/local/bin/node)
   npm    : 6.12.1
   OS     : macOS Mojave

package.jsonは以下の通りです

{
  "name": "mapProject",
  "version": "0.0.1",
  "author": "Ionic Framework",
  "homepage": "https://ionicframework.com/",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/common": "^9.1.9",
    "@angular/core": "^9.1.9",
    "@angular/fire": "^6.0.0",
    "@angular/forms": "^9.1.9",
    "@angular/platform-browser": "^9.1.9",
    "@angular/platform-browser-dynamic": "^9.1.9",
    "@angular/router": "^9.1.9",
    "@capacitor/android": "^2.1.0",
    "@capacitor/core": "2.1.0",
    "@capacitor/ios": "^2.1.0",
    "@ionic-native/core": "^5.0.7",
    "@ionic-native/splash-screen": "^5.0.0",
    "@ionic-native/status-bar": "^5.0.0",
    "@ionic/angular": "^5.0.0",
    "firebase": "^7.14.5",
    "rxjs": "~6.5.1",
    "rxjs-compat": "^6.5.5",
    "tslib": "^1.10.0",
    "zone.js": "~0.10.2"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "^0.901.7",
    "@angular/cli": "^9.1.7",
    "@angular/compiler": "^9.1.9",
    "@angular/compiler-cli": "^9.1.9",
    "@angular/language-service": "^9.1.9",
    "@capacitor/cli": "2.1.0",
    "@ionic/angular-toolkit": "^2.1.1",
    "@types/jasmine": "~3.5.0",
    "@types/jasminewd2": "~2.0.3",
    "@types/node": "^12.12.42",
    "codelyzer": "^5.1.2",
    "jasmine-core": "~3.5.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "^5.0.9",
    "karma-chrome-launcher": "~3.1.0",
    "karma-coverage-istanbul-reporter": "~2.1.0",
    "karma-jasmine": "~3.0.1",
    "karma-jasmine-html-reporter": "^1.4.2",
    "protractor": "~5.4.3",
    "ts-node": "~8.3.0",
    "tslint": "~6.1.0",
    "typescript": "~3.8.3"
  },
  "description": "An Ionic project"
}

#起こっている問題
AngularFireか、Angularが原因で困っております。

ionic serve

のコマンドで以下のようなエラーが発生します。。。

ng] ERROR in /Users/gen/node_modules/@angular/fire/angularfire2.js
[ng] Module not found: Error: Can't resolve '@angular/common' in '/Users/gen/node_modules/@angular/fire'
[ng] ERROR in /Users/gen/node_modules/@angular/fire/angularfire2.js
[ng] Module not found: Error: Can't resolve '@angular/core' in '/Users/gen/node_modules/@angular/fire'
[ng] ERROR in /Users/gen/node_modules/@angular/fire/firebase.app.module.js
[ng] Module not found: Error: Can't resolve '@angular/core' in '/Users/gen/node_modules/@angular/fire'
[ng] ERROR in /Users/gen/node_modules/@angular/fire/auth/auth.js
[ng] Module not found: Error: Can't resolve '@angular/core' in '/Users/gen/node_modules/@angular/fire/auth'
[ng] ERROR in /Users/gen/node_modules/@angular/fire/firebase.app.module.js
[ng] Module not found: Error: Can't resolve 'firebase/app' in '/Users/gen/node_modules/@angular/fire

#試したこと

npm install firebase @angular/fire
npm update

上記のコマンドを試しましたが、全く変わらずです。。。

#気になる事
/Users/gen/node_modules/以下のフォルダを確認してみました。
すると、画像のような状態でした。

正直node_modules以下のフォルダは初めて見ました。
関係あるのかわかりませんが、気になったので、、、

もしこれだけの情報で推測がつく方がいれば、お願いします！