WHD API capabilities

My Team over here is attempting to develop an internal page that pulls information from WebHelpDesk in regards to assets. These assets all reside inside the asset Info system within WebHelpDesk. We are attempting to utilize WHD's API coding to do so.

One portion of the project needs to be able to pull the PO # (Purchase Order Number) that we have placed onto said Assets. Upon looking into the API, it seems that WHD doesn't supply any lines dealing with the Purchase Order number. 

Is there any documentation or information that can be provided to us so we can continue with this project?

I have included what we are seeing on our side within the API. see word document attached.

Can anyone point me in the direction of updated/new API documentation? or even provide us with a way to see this needed information?

We have thumbed through all available Documentation that THWACK/SolarWinds provides and cannot find anything specific to Purchase Orders with the API. 

Thanks in Advance!

Asset Info API code.docx