arduino uno communication with plc

Hi, I'm doing a project on communicating PLC with arduino uno and to display the PLC data on LCD via arduino.
I need help on how to make arduino read PLC modbus register value like 40001 or 30001-2-3 etc and to display it on LCD.
The PLC I'm working on only have RS485 communication port.
Please help me out regarding hardware needed and how to write arduino code for it.

Have you done a Google search for "arduino modbus"?
Have you done any research at all?

Thanks for reply, actually I design PLC applications and know ladder programming but don’t know much about arduino and c coding, I’ve just started experimenting with it , I’m thinking of interfacing arduino with PLC to do variety of task sometime not possible with standalone plc.
I wanted to start doing it as a beginner so I can learn it, so any help is appreciated.
Also I’ve posted my query after reading several tutorials and information on this forum but without much success.