Javascript/reactnative/admob/react-native-cli/react-native-firebase

react-native-firebaseインストール

yarn add @react-native-firebase/app
yarn add @react-native-firebase/admob

package.jsonにreact-native-firebaseとadmobが入ってるか確認。

 "dependencies": {
   "@react-native-firebase/admob": "^7.5.1",
   "@react-native-firebase/app": "^8.4.5",
   "react": "16.13.1",
   "react-native": "0.63.2"
 },

参考

https://medium.com/javascript-in-plain-english/implement-admob-in-react-native-with-firebase-4e5000419109

https://dev-yakuza.github.io/react-native/react-native-firebase-admob/