react native - payment with PayPal v2/orders

I am implementing PayPal in React Native, following the documentation for PayPal Payments v2 API

Here is the step by step of my checkout:

1. Use https://api.sandbox.paypal.com/v1/oauth2/token to get token.
2. Use https://api.sandbox.paypal.com/v2/checkout/orders to create an order
3. Use approve link for clients to accept payment
4. I set the return_url to be https://www.google.com/. After clients accept the payment, I receive the return_urlhttps://www.google.com/?token=<order_id>&PayerID=<payer_id>

At this point I'm stuck: how can I use the information order_id and payer_id?