Hi Hojland,
It will depend on the expansion slot number and the channel of that slot you are using...
For example, if you fit a 1762-IF4 and make it the first expansion module - and you want to address the first analogue channel of that module, you would use I:1.0 as the address in your code (in your case, the Input address of an SCP block). The spare channels would be I:1.1/I:1.2/I:1.3.
Hope this helps!
Regards,
Rob