Finger numbers are very helpful when playing the piano. You will always use them no matter what level you are. Some beginner books have you practice by reading only finger numbers.
The piano keyboard is a repeated pattern of 12 notes. There is a solid row of white keys (52 on a full sized keyboard) and alternateing groups of 2 and 3 black notes (36 total on a full sized keyboard).
Practice naming the pitches with the exercise above. Remember the music alphabet has the letters A-G!