[Vuejs]-WARNING in ./src/main.js 6:8-15 "export 'default' (imported as 'vuefire') was not found in 'vuefire'

From the documentation, I think you want the import line for vuefire to be this, as the vuefire package doesn’t have a default export:

import { firestorePlugin } from 'vuefire';

(Alternatively you might need rtdbPlugin instead of firestorePlugin if you are using the realtime database and not firestore, more here)

And when you actually call Vue.use it should look like this:

Vue.use(firestorePlugin);