HEX is just a format of this data; in DEC this is 1112407080992, in OCT is 20140050200040, and in binary is 10000001100000000101000010000000000100000. It is a different representation of the same data.

Your question about protocol depends on the devices you will communicate with. Where do you send this data?

Best regards

Actually, you don't want only to send data, because Function code 03 you are using is used to read output registers of Modbus slave, 32 words starting at register 161. So you will also need to read the response from this slave.

I don't have experience with CP341, but I used ET200S SI module, and it should be similar. You first need to send this you have data using FB3 (S_SEND_SI) - this is request to read. After this FB signal it is DONE, you need to call FB2 (S_RECV_SI) to read the response and place it in some DB.

Maybe CP341 uses different function, but procedure should be the same. Check this manual for more info: http://support.automation.siemens.com/WW/view/en/25362836

Best regards