The sentence with the modifying phrase placed incorrectly is:
"Maddie wants to buy new soccer cleats from her favorite store once she saves up enough money, Soccer Nation."
In this sentence, the phrase "Soccer Nation" is placed at the end in a way that could lead to confusion about what it modifies. It would be clearer to rephrase the sentence to indicate that "Soccer Nation" is the name of the store. A possible revision could be: "Maddie wants to buy new soccer cleats from her favorite store, Soccer Nation, once she saves up enough money."