1 day interval type = pedal close to max for 3-10 minutes coast for 3-10 for 45+, i.e. mtbing
1 day long and steady at about 60-70% max for 90 minutes+ i.e. road riding.
1 day whatever you want, cruise, fun, fast, improve skills for 45+ minutes.
You can do both types of training on the trails but mtb for strength, road for stamina, is by nature more prone to provide that type training. It's also a good idea to do some body weight exercise like push ups, pull ups, sit ups to gain core and upper body stength.
After a few weeks and as your stamina and strength improves, up the #s and intensity. Don't know you or yourr condition, but most people can push themselves harder than they think or thier mind lets them. It might seem a bit gay, or useless but stretching after, and a warm up before will help with pain and recovery, allowing you to push harder next ride, and that warm up before will also improve that ride. Even if your warm up is just to take it light the first few miles. It's a good rule of thumb not train too hard for moe than 2 days in a row, then take it easy for a day. IMO it's good to take off 2 days in a row each week or atleast no pushing on those days.
Training, diet, and rest = best progress. Skimp on any 1 and your progress will slow.
Look into lactic, or anaerobic threshold training. Aside fom skill, on longer races it's what seperates the winners from the losers. Especially the mental part of it.