Calculating Radial Velocity from Hipparcos
You cannot calculate the radial velocity from a proper motion. The proper motion is the motion you see the star move on the sky, so perpendicular to your line of sight towards the star. The radial velocity is the velocity of the star along this line of sight. Perhaps this picture will help:


https://en.wikipedia.org/wiki/Proper_motion

Radial velocities are actually calculated by measuring the Doppler shift of the spectra of stars, but this is not very easy, and you need the raw spectrum data. You are probably best off just taking the values of the radial velocity from that site for example.