how to use "to do" or "to be done"?

The tree is not going to decorate anything with accessories, but it itself is going to be decorated with the accessories, so the Second one "This tree is moved to be decorated with accessories" is correct. and IS or Was depends on what the speaker intends to convey, If He/she refers to past action then "Was "will be used.. I hope this explanation answers your query.

To do/ to move - infinitive in active voice to be done/ to be moved - infinitive in passive voice

The verb MOVE is transitive (They moved the tree.) and intransitive as well (The tree moved in the whirlwind.)

To the question 'which is correct?' ...to decorate with accessories..., or to be decorated with accessories. It is the latter, because someone is to decorate the tree; and the tree is to be decorated by someone.

I think there is a slightly larger issue here, neither sentence are good grammar since they mix both present and future tense:

"This tree is moved..." - by something that is happening NOW. The wind? "...to be decorated with accessories." - by someone in the FUTURE.

[I am going to move the tree] "...to decorate [it] with accessories." is a statement of intent (Active voice), either now or at some time in the future.

"The tree was moved by me [yesterday]", is an explanation of what I did at some time in the past (Passive voice).

ACTIVE VOICE: The cat ate the rat. The cat acted upon the object (the rat).

PASSIVE VOICE: The rat was eaten by the cat. The object was acted upon by the cat.

If a sentence includes the word "by", it is PASSIVE VOICE.

If your original sentence is a question, it is better asked as:

"Should this tree be moved [to a different location in the future] to decorate [it] with accessories [In the future]?"

This is either a non-directed or a rhetorical question - it is being asked to anyone within hearing distance, unless you name someone: "John, should I move...", or it could be a question one asks oneself, when pondering the benefits of moving the tree.

The assumption is that, if I put the decorations on here and now, will it cause a problem? / is it easier / better for me to do this somewhere else?