I'm assuming you live in a place where plumies can be planted inground and require no winter protection. If not, you'd have to uproot in winter or else it'd surely die. Cumbersome to deal with a big tree (2" dia. trunk) though some people do just that. I don't. I keep potted so easier to bring in garage when needed.

If weather not a constraint, take out of pot and plant like you would and other plant.

two inch diameter is not bad. Most of the roots radiate out unless it has a tap root or was previously in a pot. At least a beach ball size root ball will work. I would go about a foot around the trunk and try to get about a foot or slightly more deep.

Thanks for advice, y'all. Shouldn't be a problem here in San Diego. I will do it this winter and let you know how it goes. It is my favorite color and flower thickness and I didn't want to kill it. I am digging it out of the ground. Do Plumerias have a tap root? I hope not. I will photo as I do the deed. aloha

Good luck. It will only have a tap root if it is a seedling or is grafted to seedling stock. Even then the tap root is not as strong/problematic as other types of plants.

Great. Thanks. It will break easily if it is there.