I am a newbie, and this is probably a simple question, but I have a new Trek Domane 2. It is the 2020 model. I from what I can tell from the Trek web site it has a Shimano Claris R2000, 8 speed shifter, and based on the back tire there are 8 gears there so I think that is correct. In the winter want to be able to ride the bike on my wahoo kicker. When I went to the bike store the only cassette they had was the Shimano CS5700 11-25T which is a has 10 gears. I've adjusted the tension on the derailleur, but that doesn't seem to do anything. The 4 big gears and the small one seem to work, but not the other ones. What do I need to do to fix this?