Canon MultiPASS C3500 User Manual page 262

If you need to contact Canon directly, make sure you have the following
information:
Product name—MultiPASS C3500
Serial number
MultiPASS Desktop Manager version number
Place of purchase
Nature of problem
Steps you have taken to solve the problem and the results
The serial number is located on the label on the back of the unit:
The version number of MultiPASS Desktop Manager is included in the
About information. In the Desktop Manager, click Help and then click
About.
10-2 Troubleshooting Chapter 10