You probably have the SDK version 9 installed but use SDK version 8 syntax.

You have 2 options. Addopt the new SDK to use the old syntax with importing your firebase like this:

import * as firebase from "firebase/compat/app"
import "firebase/compat/auth"

const firebaseApp=firebase.initializeApp({
    apiKey: process.env.REACT_APP_FIREBASE_API_KEY,
  authDomain: process.env.REACT_APP_FIREBASE_AUTH_DOMAIN,
  projectId: process.env.REACT_APP_FIREBASE_PROJECT_ID,
  storageBucket:process.env.REACT_APP_FIREBASE_STORAGE_BUCKET,
  messagingSenderId: process.env.REACT_APP_FIREBASE_MESSAGING_SENDER_ID,
  appId: process.env.REACT_APP_FIREBASE_APP_ID
})
export const auth=firebaseApp.auth()
export default firebaseApp

or

use the new syntax:

import { initializeApp } from 'firebase/app';
import { getAuth } from "firebase/auth";

const firebaseConfig = {
  //...
};

const app = initializeApp(firebaseConfig);
const auth = getAuth();