Find the migration of the tables and classes from AX 4 or AX 2009 to AX 2012

Hi!.

I have a problem to find a class into AX 2012 because this class dissapear and i don't find why this class dissapear.

So, exist a document to see the transformation of tables, classes,etc in AX 4 or AX 2009 to AX 2012?

The class is InventItemUnitConvert and use the table UnitConvert

Thanks for all!

Sorry if my question it's a dummy question, i'm new with AX 

Regards

Eduardo Rotundo