MKCoordinateRegionMakeWithDistance
can be used to make a region with a specified distance (in meters).
Here is the method signature:
func MKCoordinateRegionMakeWithDistance(_ centerCoordinate: CLLocationCoordinate2D,
_ latitudinalMeters: CLLocationDistance,
_ longitudinalMeters: CLLocationDistance) -> MKCoordinateRegion
Use an extension to get your desired distance and convert it into meters.