How to calculate probability of finding an electron at a point?
Consider the 1D case for simplicity.

The modulus square of the wavefunction is interpreted as a probability density in the sense that
$$
|\psi(x)|^2\mathrm{d}x
$$
gives you the probability of finding the electron in within $x$ and $x+\mathrm{d}x$. Now if you want to consider the probability to find the electron exactly in $x$ you have to take the limit $\mathrm{d}x\to 0$ and this gives you zero probability. Formally, this corresponds to compute
$$
P(x=x_0) = \int_{x_0}^{x_0} |\psi(x)|^2\mathrm{d}x = 0,
$$
which is zero since the limits of the integral are the same. Therefore there is $0$ probability to find an electron at exactly one point.