I assume you currently have a line voltage (240V) thermostat. If that is the case the Home Depot has this thermostat as an example. There is not a big selection of line voltage programmable thermostats.

The wiring is simple, but you have to be very careful if you are doing this yourself. You have to make sure you shut off the power. If you have doubts then hire an HVAC company to do it.

Sorry I wasn’t clear. There is no thermostat at all in this room.

The main part of the house (built 1978) is on a heat pump w/auxiliary electric heat and has a thermostat as you’d expect.

This room is an addition that was built in 1987. All we have are baseboard heaters with an individual ‘dial’ - not a real thermostat. There is no wall thermostat.

I want to hook all three of the baseboard heaters up to a single thermostat. Part of the issue is that I don’t even know where the wires run through the wall.

Then I suggest calling in an electrician to determine how the wiring can be routed to a common point so that the baseboards can be controlled by a single programmable thermostat.