None in the sentence.
I is the subject
am is the verb
happy is an adjective. It describes I (I am a happy I)
to see is an infinitive phrase. It is is not acting as a preposition.
you is the object of the verb see.
There isn't one. Don't confuse an infinitive with a propositional phrase. An infinitive is a verb form. A prepositional phrase is a noun form.
