Cubase has a very poor method of MIDI channel management unfortunately.
What you need to do is go into the “Inspector” of a track that you want on a specific MIDI channel and open the “Input Transformer”, then select “track”. Then open the panel and select the factory preset “Channel 1 only” (or whatever channel you want on that track) from the channel filters.
Make sure that the preset is checked as “on”.
If you make a channel filter for channel 10 on the track you want to receive your pads, this should do it.