Hello Eniola,
The 26XX line of SMU's do not take SCPI commands. We utilize a command set known as TSP (test script processor) which operates in a similar way. I'll link the reference manual below,
see page 2-51 and on for sweep functions and there are examples provided as you read along. Specifically,
see section 9 for all TSP commands.
Additionally, I would recommend downloading
TSB (Test Script Builder) which will allow you to program and run commands remotely. In the navigator pane on the left hand side, you can find examples for a linear IV sweep example which would help you to start building and customizing your setup once you've read the sections I recommended above.
Here is the reference manual:
Series 2600B System SourceMeter Instrument Reference Manual | Tektronix
Here is link to download TSB:
Keithley Test Script Builder | Tektronix