in_app_purchase how do I get the data needed for android verification from the serverVerificationData

I am trying to implement server side verification for IAP's in my flutter app. I am using the package

https://pub.dev/packages/in_app_purchase

version: ^0.3.4+8

And I am confused how I get the data to verify my purchase for android and IOS. In the documentation they say

"or verify the data using your own server with serverVerificationData."

This string seems to return some kind of encoded string. How do I then extract the needed data from this string?

Android needs a package name, purchase id and purchaseToken. And Ios needs a object receipt-data. I am confused on how I am to get that data from the serverVerificationData string.

I am currently implementing android first.

from in_app_purchase how do I get the data needed for android verification from the serverVerificationData