Hey there KarenDavis,
Welcome to the Nest Thermostat Community! Based on that wiring alone, we may need a bit more information. Would you be able to post a picture of your wiring set-up? I would also encourage you to read this article on Nest Thermostat compatibility, as it would also help you see if your HVAC system is compatible as well.
I look forward to your response, and if you have any other questions or concerns for me, please let me know!
We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.