Emily is turning 4 tomorrow

This morning I went in to wake up Emily and reminded her that her birthday is tomorrow. She says what number am I? Which if you speak Emily, it means, how old am I? I tell her she is three, but will be four tomorrow. She then says, I don't know how to be four. I try my best not to laugh and tell her that she just has to be herself, and that she can do everything she did when she was three, but that she will be learning many more things as a four-year-old. The things she says sometimes.