If the wavelength of one wave is 0.25 or ¼ meters, how many waves will be formed in one meter?

4 waves will be formed.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.