AR Foundation update old project from 1 preview22 to 3.1.0 preview1 - Error CS0234 & Error CS0246

Hi Guys

Can you shed some light on these please. Besides clearing the console, what do I need to do to get rid of these?

Old project was Unity 2018.3 with AR Foundation 1.0.0 preview22, now upgraded to 2019.3 beta AR Foundation 3.1.0 preview1.

Build settings is currently set to Android

 

OK for others having same issues, I found this migration from version1 to 2 post usefull
In the 1st post from this thread, there's some clues
https://forum.unity.com/threads/ar-foundation-2-1-now-available.678979/

That leads to a migration guide:
https://docs.unity3d.com/Packages/c...90.2000986238.1574580476-416189254.1557059478

Sorted all my warnings and errors.

I'm now just down to "placeonplane" which I heavily customised. I may need to completely redo this script from the latest samples. It'll be quicker to add my bits, than figuring out why the old bits dont work