Take a look at the nutrition label. Find the number of grams of protein per serving about halfway down. Then find the number of grams per serving at the top. Divide the grams of protein per serving (the smaller number) by the grams per serving (the larger number). That gives you the protein percentage of the flour. If it's in the neighborhood of 10%, you have all-purpose flour. If it's below 9%, you have cake flour.

By baking flour, do you mean regular all-purpose flour? If so, they are not the same. Cake flour is a finer, starchier flour with less gluten than all-purpose flour -- it's ideal for cakes, as it yields a nice, tender crumb.