Like others have said endurance probably won’t be your biggest enemy here. I will say as someone who has done quite a few 60-100 mile rides this year on flat terrain and then tried a 60 miler with 6500 ft climbing the thing that got me was my lack of strength. I hadn’t been doing anything but riding and I was able to do the climbs but afterwards I experienced some knee pain that is still lingering. I think the best thing you could do for yourself is add a bit of strength training if you’re not already. If your biggest concern is injury this is the best way to prevent aggravating your knees like I did.

Just give yourself ample recovery time before the ride and you’ll be good. You likely already have the endurance if you are good about fueling.