What Are Some Good Books To Improve A First-grade Reading Level?

I’m giving a few books to a girl who is in third grade but has a first-grade reading level. Should I give her first grade books, second grade books, or third grade books? What’s going to improve her reading level? Does anyone have any suggestions that I could easily find at Barnes and Noble tonight. As for the type of book, anything goes, but I want 1 or 2 books about puppies because that is one thing that I know she likes.