I have a split unit with a furnace but when I remove my thermostat it only shows 2 white wires and 2 red wires. How can I put my thermostat or do I have to rewire it. I have a digital thermostat but they told me does won't work

The old tstat is marked as to what each post does,r,w,y,g, label each wire as you take it off as to where it went and put the wires on new tstat the same way