This script shows how to use PowerShell to invoke a Jenkins workflow and retrieve the result.
Finding the results is depenent on each request being submitted with a unique request ID that may be filtered for. It also assumes that a unique API token for the workflow being called is known.
Unfortunately, the best that can be retrieved at the completion of a Jenkins job is the text based log file. This resides in a known folder on the jenkins server to the workflow can be hacked to replace the log with something a little more workable like JSON output.