What kind of training plan to prepare for this?
Plan Builder is largely meant to handle this. If you want a bit more DIY, the article below and some blog posts are worthy.
There could be a big difference in how you prepare based on your goals for the event.
If you are riding near the front of the pack and “racing” the demands are going to be much different with potentially a lot of VO2 max and threshold work.
However if you simply are going out to finish the day and have a fun time, then endurance and tempo are likely going to rule the day.
Here’s a link to a great post from @brendanhousler on the subject:
throwback! just added some quick updates, and I’d also add Over Unders for sure!! Podcast on that coming on Tuesday