Answer:
The 'to' is part of the infinitive verb form. It is not a preposition.
Explanation:
Remember this:
If a verb follows the word 'to,' then it is an infinitive. If the word that follows the word 'to' is an article, a pronoun, or a noun, then the 'to' is a preposition.
prep. infinitive
I went to the store to buy a car.