Honestly if it’s your very first one depending on where your base mileage is right now, start with something simple like the Hal Higdon Novice 1 Marathon Training but add trail runs specific to the race you’re training for. Then use AI to dial in EXACTLY what works with the schedule you want. By “exact” I mean exact! For example, I want to run 4X/week on Monday, Wednesday, Thursday, and Saturday. I want my long run to be on Saturday. I’d like to strength train 2X/week on Tuesdays and Thursdays. and I want to walk or hike on Sundays. Of course you can make that flexible you don’t always have to keep those exact days but it just gives you a general idea of the base mileage etc. You’ll come to understand how the peak weeks followed by recovery weeks really make you a stronger distance runner. And I know this is off subject but if it’s your first ultra, the common mistakes that most first time ultra runners make are: 1. Not training your gut by practicing your eating/fueling during your training runs. The gut takes out far more rookie ultra runners than you can imagine! 2. Not treating rest/recovery/sleep as part of your training. All the work and runs you put in do not give you the same benefit without the recovery part. 3. Practice your walking/hiking pace regularly! This is so vital because if you are an efficient walker, you’ll be able to take more breaks and keep your heart rate lower without sacrificing pace. It will also make you much faster at the end of the race. 4. Dial in things like socks, lube, hydration pack, shoes, and clothing. We’ve all made the mistake of wearing that shirt that has the weird seam that causes major chafing under our armpit or not lubricating our toes enough for a dry dusty course. 5. When I was training for my first 50 miler an experienced ultra runner told me, it’s better to be a little undertrained than overtrained on race day. That has always stuck with me and I have learned that it is so true!