For obtaining the probability distribution we should take the absolute value of the Schrodingër Wave Function 'Ψ'and then square it. But why to take first the absolute value if the square is going to give us a positive number anyways?
This is because the values of the wavefunction are complex numbers. Squaring a complex number doesn't necessarily give you a positive number, or even a real one. For example, $i^2=-1$, and $(1+i)^2 = 2i$.