How do I find the invoiceID?

How do I find the invoiceID?

my invoices are created using the proper code in Zoho Creator.  I want to do some additional stuff with the invoices as shown here: https://help.creator.zoho.com/Get-Invoice-Info.html   but i do not know where to find the InvoiceID (which are auto-generated [im not passing a custom variable through]). 
 
How would I use the link above without first knowing the InvoiceID?