Answer:
to inform
Step-by-step explanation:
The author is not trying to entertain because entertaining would be like to add more detail and description, and generally just create a story.
The author is not trying to persuade because they don't give any reasons to why you should do something or not; they don't state an opinion.
The author is trying to inform because they are giving us information about the young girl and that her note to her parent's is about trying to tell them why they should buy a puppy.