This is how the Admin Console looks like when multiple instances are deployed
You go into Adobe Campaign and you'll see the list of instances
You go into each instance and you've got the list of users which you can extract by copy/paste by 100 form the screen or you'll go into each Product Profile and you can extract users for each Product Profile then externally you would have to aggregate all the files into one.... The user list itself under Product doesn't allow you to export, just add but if your list of users sin't too long, copy from the screen and paste it in Excel works pretty well, also not as neat as a direct export.
Since user management is made in Admin Console, you're best option would be in the Admin Console by export all users and then filtering the resulting CSV file to include only your ACS Production instance.
To have the export menu at user level, you would need System Admin role. Otherwise with Product permission you would have to do through each of your ACS instance and the export menu should be available too