What is prefab:
https://docs.unity3d.com/Manual/Prefabs.html

In your case, you will get an additional sphere in the root of the hierarchy, which is not a marker.

I'm messing around with 3D markers.
So i created a 3D marker by code using:

GameObject Sphere;
OnlineMapsMarker3D marker3D;

marker = OnlineMapsControlBase3D.instance.AddMarker3D(new Vector2 (xV2, yV2), Sphere);

i have looked around the forums and i see people use names like prefab I'm not so used to using prefabs but yeah i have my sphere as a prefab but it wont take my prefab out of my project folder, i have tried
Sphere = GameObject.CreatePrimitive(PrimitiveType.Sphere);
but that will create a sphere as a separate gameobject, not as the markers prefab. sorry for the newb question.