Hi, will be slightly difficult since there is nothing in the current documentation before 8.13.4 for the upgrade path.
About as close as you are going to get is this old post on the forum:
and even that link only goes as far as 8.8. After that, I would recommend doing all of the point releases between 8.8 to 8.13.4 and then follow the upgrade path as per this link:
and the upgrade docs here:
those links should have all the information you need to do each step-by-step upgrade for following the upgrade path.