[Sirtel]

You don't need to add the series number to the title with a Kobo. Kobo takes the series information automatically from Calibre. Kindles don't have any series information for sideloaded books, that's why they needed that plugboard, but a Kobo doesn't need it.

You have to connect your Kobo to Calibre twice to get the series info transferred - first, send the books over, eject, let your Kobo process them and then connect again. After ejecting the second time, you should have your series on your Kobo.

Edit: forgot to add that the metadata management should be set to Automatic in Calibre.