Not sure if my unit is comparable looking to get Rachio 3. Just want to make sure. Have 6 zones
Looking at the manual, you are looking at an easy conversion ahead of you.
All of your valves are 24VAC (good) and you don’t have a master valve (so don’t worry about it).
You can disregard the battery connected via the red & black pair on the right.
You will also be using a power supply which came with your Rachio (unless you live within a country with a 220V power) instead of the two thick brown lines connected the the two leftmost terminals, so disregard those as well.
To convert, move the white line from your old controller to any of the C terminals on your Rachio.
Move the other 6 thin zone wires (brown through yellow) to any of the numbered terminals on your Rachio (1 through 6), do not worry about which one goes where as you’ll be able to take a photo and name each of the zones during the setup.
When the app asks if you have a master valve, answer is that you do not.
You are welcome to ask more questions as they come up. Welcome to the community