This is a #PowerShell script I picked up along the way (not OP) and use often for an output of all the workflows in a farm. Regardless of its origin (Nintex of SP). You save this script function as a file named Get-SPWorkflow.ps1 and use it by calling in PowerShell .\Get-SPWorkflow
If you provide the optional boolean parameter, you can have the output displayed in the console. If you leave it out or provide $true, then you will be prompted to provide a path to save the output to. Then let it go.
It will output all list workflows in the farm with the site URL, list title and workflow name. It will also provide a count of the number of sites that have workflows as well as the number of lists.