Hello yorelisg;

Do you mean you want to connect to your M340 using Modbus/TCP, over the integrated Profinet port of your PLC?

Which CPU are you working with?

An S7-1200 or S7-1500 CPU has integrated functions for Modbus/TCP communications, without requiring extra hardware or software.

Modbus/TCP with instructions "MB_CLIENT" and "MB_SERVER"

https://support.industry.siemens.com/cs/ww/en/view/102020340

S7-400 and S7-300 CPUs must use OpenModbus TCP libraries to use the integrated Profinet interface (or an extra CP 343-1 or CP 443-1) to exchange with Modbus TCP. Information on the OpenModbus TCP blocks and licenses is available in the last link of this application example.

Communication between SIMATIC S7 and Modicon M340 via Modbus TCP

https://support.industry.siemens.com/cs/ww/en/view/38586568

Hope this helps,

Daniel Chartier