Since we are just being asked about giving the angular velocity (ω) of the rotating wheel in rad/s, we do not need to take into account the diameter of the wheel.
We only do that when the linear velocity is being asked. v=rω
So we are given with
and we want to make the unit as
In order to do that, we just have to remember that 1 revolution=2π rad
Doing the necessary conversions:
By doing the arithmetic you will be able to get the value of the angular velocity in rad/s.
Hope that helps.