Train muscles for cycling?

Hello, I have two questions for the cyclists,

I'd like to start cycling longer distances. I'll be out for about two to three hours at a constant speed (initially on a regular road bike), so I'd like to know if I should also train on other fitness equipment in the gym to gain more strength over time.

And I would be interested to know whether you need a lot of muscle mass for that kind of time per route or even longer rides, or whether you need less and a lot of stamina.

Hope the questions are understandable 🙂