When viewed from an inertial frame of reference, a particle of mass...

Centrifugal force is a pseudo force which is experienced only in a non-inertial (rotating) frame of reference.

When viewed from an inertial frame of reference, no pseudo forces are present. The particle executes circular motion solely due to a real centripetal force of magnitude $\dfrac{mv^2}{r}$ directed towards the centre.

Thus, the centrifugal force acting on the particle in an inertial frame is zero.