What child resources are available to you from the service information page:
I see in your other post, Watch ArcGIS Server directories on a service change , you listed a directory for 10.3.1:
The correct answer (tested on 10.3.1 version) is
arcgisserver\10.3\config-store\services\folderName\<service name>.MapServer\<service name>.MapServer.json
Are you using 10.5.1 or 10.3.1?
This is something we added at 10.5 to support incremental backups, so yes, it won't be available at 10.3.1. Since you are upgrading to 10.5.x I would wait to implement anything, but that's up to you.