Hi, you get in the response the "Response payload" returned after a successful call with either the PayPal authorization ID or the pay key to process via REST (PAY-XXXXXXXXXX). Or once the authorization is processed you then can log-in into your PayPal profile and capture the payment from there.

If you open the developer tool/console (F12) just before you click the payment button then check into the Network tab and you will find the Response Payload in the response  area, attached image. This is returned in the response so you can use the response payload.