***** NOT A TEACHER *****
Hello, Par:
Since this is not homework, I believe that we members are allowed to comment.
1. When you get time, you may wish to check your books and the Web for the difference between an ADVERB and an ADVERBIAL. I know that it can be very confusing.
2. Sometimes it is easier to parse (analyze) a sentence if you put it into its regular (usual) order:
"A mysterious tree had appeared in the woods one summer day in Frog Creek, Pennsylvania.
In my opinion, I think that your sentence should be parsed like this:
a = adjective (determiner).
mysterious = adjective that modifies (describes) "tree."
tree = noun,
had appeared = verb.
in the woods = prepositional phrase. As you said, it tells where it appeared. And as a teacher in this thread told you, the prepositional phrase is counted as an adverbial, not an "adverb."
one summer day = a noun phrase that is also adverbial. It modifies the verb. It tells when. Sometimes nouns are said to modify verbs. For example: It happened Monday.
in Frog Creek, Pennysylvania. = same explanation as for "in the woods."
3. "The tree house was filled with books, and it was magic."
the = adjective (determiner).
tree = noun that is being used as an adjective to describe the house.
house = noun.
was filled = (passive) verb. "Someone filled the tree house."
with books = prepositional phrase. Not an "adverb" but an adverbial.
I do not understand what you wish to express when you add "and it was magic."
Is it possible that this time you are looking for a genuine adverb? Do you mean something like this:
"The tree house was magically filled with books."