Gentlemen,
Thanks so much for your quick responses. Your suggestions have both been very helpful. I've got the solution now.
Using the Object Model browser allows me see all parameters/values. Using the brackets [] to denote a specific item in a list is the way to go.
I ran into a slight snag using them with curl:
However, a StackOverflow post https://stackoverflow.com/questions/8333920/passing-a-url-with-brackets-to-curl about using brackets in curl solved the issue: pass in a -g flag to turn off the URL globbing parser https://curl.se/docs/manpage.html#-g.
Now it works perfectly:
Thanks again for your help,
Mike