Pls help me write code from this datasheet, I want to use just Temp Humidity and pH.
From the limited information you have provided, I'm assuming that you have one of those 3 (or 5) prong NPK sensors that uses modbus over RS485 to communicate with it.
Search the forums for NPK Sensor and you should find code to get you started.
You might want to tell us which Arduino you are using.
Also note that the general forum opinion is that those NPK sensors don't do what they claim to do - assuming of course that is what you have.
Here are two thorough, similar, procedures for using registers on an NPK sensor. The second link has very complete comments in the code, but uses another serial library.