A PathFollow3D node HAS to be a child of a Path3D node
Add a PathFollow3D node as a child of your Path3D node.
Turn off the Loop property
so that objects following the path
will stop when they reach the end.
We will control the progress with
Create a model for an enemy to follow the path
Add a MeshInstance3D as a child of the PathFollow3D
Choose a new CapsuleMesh and adjust the properties as shown
Set the y value of the mesh transform to 1.5
to raise the capsule to road level
The next step is to turn our PathFollow into the Enemy Scene so that we can attach a script