The number of wires coming out of your wall will tell you how many wires you need your thermostat to have. If there are 2 wires, you need at least a 2 wire thermostat. Having extra wires is fine; if you have 2 wires in your wall and purchase a 4 wire thermostat, you can leave two of the ports in the thermostat empty and it will still work properly. Having not enough wires is not OK; if you have 4 wires in your wall and purchase a 2 wire thermostat, it will not work. Play it safe, count your wires before you buy a new thermostat.
Thermostats can be found at www.supplyhouse.com
