The backend thing has nothing special with native base or plain react or other library, it's all react.
You connect to your backend mainly with REST (or graphQL), may be other custom things like firebase.
We use only REST.
To work with REST services you can use axios or fetch (we prefere axios). Everything is asynchronous, so you must know what promises are.
Finally, you'll end up using redux with some library to cope with promises, we use redux-promise-middleware, redux-thunk and redux-saga, in that order.
Sometimes plain react state may be fine.