Answer:
on Tuesday
Step-by-step explanation:
A modifier is a word, phrase, or clause that describes or adds more information to another word, and they act as adjectives (they modify nouns), or adverbs (they modify adjectives, verbs or adverbs).
In the sentence, "on Tuesday" is acting as a modifier, more specifically, as an adverb because it modifies or adds more information to the verb "go". When would Erin (she) go to the store? On Tuesday.