Answer:
Shoes.
Step-by-step explanation:
A prepositional phrase comprises of a preposition followed by its object and any/or modifiers that function to modify the object.
Object of preposition is characterized as the noun or pronoun that is followed the preposition in a prepositional phrase and functions to accomplish its meaning.
In the given sentence, the object of preposition is 'shoes' in the prepositional phrase 'of shoes' as it is following the preposition and functioning to complete the meaning of the phrase. Thus, 'shoes' is the correct answer.