no placeable prefab?

I've been following this tutorial to learn how to place objects in ar:

But I've come across a problem.

From video:


My project:


For some reason I don't have the Placeable Prefab section in my SpawnObjectOnPlace(Script).

I just started Unity perhaps a week ago and I know practically nothing about coding, I just tried following the video step-by-step so if I'm blinding on something that's my bad.

Just in case here's the code I copied from the video. Any kind of help is much appreciated!

 

Make the placeablePrefab property `public` rather than `private`.

 

Thank you for the reply but the Placeable Prefab is still not visible.

I rewrote the code just to be safe, is there anything else I could do?

 

And now I'm also getting these errors, any idea why?

 

you are missing the Monobehavior word?

Code (CSharp):

1. public class SpawnObjectOnPlane : MonoBehaviour

you can't use Awake(), update(), etc. without the MonoBehaviour word