Hi,
In Guru -> Settings -> Api - Orders Details, you can find the API options, you can generate a new secure KEY and then you need to save this page. After this, a new URL will be visible for this option - "API URL" and this URL will be used to access Guru API.
The result is a JSON with all Payed orders or, if you select a specific "Pament Plugins", the result will be a JSON with all Payed orders with that Payment Plugin.