Working in the food business for many years, usually refrigeration units that size do not have an "on/off" switch. Most times they are hard wired (no plug) and there is an emergency cut off switch somewhere in the vicinity. Being that size system in a commercial setting, I would say it's a 220v system, but you won't know until you look at the connections.
If the unit is 220 volts and it is hard wired, you probably can retrofit a plug onto it, just make sure the wire you use for the plug is rated at or higher than the AMPS this sucker draws. As for on/off, just unplug it when not in use or install a 220v cut off switch like they have for AC compressors.
It looks like the unit is an "all in one" meaning the compressor is built inside of it (good thing), I see the compressor vents under the ice maker. If it were a remote unit where the compressor was separate (usually in the basement of a bar) you would have had one big headache on your hands and a bigger cost.
As with any refrigerant device, once you get it to where it will reside, give it a few hours for the refrigerant oil in the system to settle before plugging it in.