Here's why:
* Infinitive phrases start with an infinitive, which is the base form of a verb preceded by "to" (e.g., "to go," "to shop," "to eat").
* The sentence "Johnna went to the store shop" has the verb "went," but it doesn't include an infinitive.
It's possible that the sentence is missing a word, or the intended meaning is different. For example, the sentence could be:
* "Johnna went to the store to shop." This sentence uses the infinitive phrase "to shop" as the purpose of Johnna's trip.
Without more context, it's hard to determine the intended role of the infinitive phrase.