Help required install an oil fired Camray 5

[YooFlo]

Hi , I have an old trianco oil boiler, outdoor, and I want to change it with an indoor camray 5 . The first thing was that I thought it will be a simple swap in between them, but turned out it’s not really like that. First of all the installation on the old trianco has just a pump and a room thermostat, it doesn’t have 2 way valve or hot water cylinder connected. The difference between the two boilers is that the old trianco has a cable with 4 wires and the camray5 a cable with 3 wires and this is where the problem comes as I do not know how to connect the camray 5 to the room thermostat, I definitely can connect to the pump and power , but how do I connect the thermostat please? The thermostat is a Honeywell one with 3 wires at the moment , but I would love to have it charged with a Hive one if is possible. I would really appreciate if anyone can help me, thank you .