Convertt c# twincat ads software in to modbus (c# or flutter)

I am looking to convert my existing TwinCAT ADS software into the Modbus protocol using C# and Flutter. I JUST NEED TO CONVERT A SMALL PART OF THE SOFTWARE, I AM COMMIUNICATING WITH BECKHOFF BC9000, My existing software needs to be converted so I can make use of the Modbus protocol that is available with my hardware. I need assistance with converting the different protocols and making sure the code has been written correctly to ensure the software works as expected. Additionally, I am also looking for help with testing the software to make sure it performs as needed. Please let me know if you have extensive experience in dealing with both C# and Flutter and have had success with software conversions. Thank you!