@moncon - if you bought a Rachio enclosure there is a hardwired connection to a plug inside the enclosure that one then plugs the Rachio transformer into.
The Rachio runs off of 24 VAC, not 120 VAC. One can cut the Rachio transformer cable and splice in a longer run (I’ve done this on one install) so that the Rachio transformer can be plugged in someplace - in the event the box that was purchased doesn’t have a plug receptacle.
Welcome to the Rachio community.