Hi I have a large-ish Jade tree which had white mold under its bark, please advise

Please post a photo that shows the entire plant, including its pot. Anything that has penetrated the bark is a serious problem.

Here is what I got

-- The whole of it

-- close up view

I can't see the second photo clearly to see mold. I hope you are able to figure out what the issue is and save the plant but overall, it does not look good.

I believe the problem is with the roots. It is potted in a very unusual and overly large container that I suspect may not have drain holes. That is a recipe for root suffocation. When the roots are in trouble, then they are no longer able to supply the plant with the water and nutrients that it needs and the plant then dies. It looks like yours is too far gone to be saved.

Out of curiosity, when and why was it put into that container?

Wow! My first time to see a seriously deadish looking jade!

Have you tried to cut off a portion of any of the branches, just to see if there is still some green life in it. If there is none, It seems like it is beyond redemption/recovery. Checking the condition of the roots will help too if you want. They have such shallow and small root mass that easily succumbs to root rotting when left in a very wet media or in a container with no drain holes. Seeing that there is not even one leaf left that maybe you can try to leaf propagate as back-up indicates to me something occurred first at root level for it to be unable to sustain even a few leaves.

You have successfully killed this plant.
Try to do some research regarding the care of jade plants and try again. We will be here to answer your questions. But jades are succulents which like to be drier at the roots and a bright location. Not many plants tolerate being over potted.
Plastic and clay pots are cheap enough to avoid using a square plastic pail.