Answer: Hi there! I think that the preposition in this sentence would be "near".
Explanation: A preposition is a term that often describes how, where, or when something is being done. Whenever you want to figure out what a preposition in a sentence is, use the following sentence and you'll eventually find which word is your preposition: the mouse goes ____ the box.
Your preposition would look like this in the mouse sentence: the mouse goes NEAR the box.
I hope that this helps you out!