You take the ISO and burn it to a disk or you take the USB image and flash that on a thumb drive and reimage the appliance.
I used the USB to reimage the boxes. My actual requirement is to delete the existing configuration and make the box look new. Is there a command available?
There is no supported method of resetting the configuration other than reimaging the appliance.
The only other method i can offer is to backup the default policy on a freshly imaged appliance and restore it to another appliance. However, this only affects the policy. It does not affect the appliance configuration section and leaves all the network settings and licenses and dashboards in place.