Can't build the game

[DavidCodesDev]

I get these errors when trying to build the game:

Assets/unity-themes-master/Codebase/Systems/Event/EventStepper.cs(7,8): error CS0246: The type or namespace name `Interface' could not be found. Are you missing an assembly reference?

Assets/unity-themes-master/Codebase/Supports/Utility/UtilityPref.cs(8,8): error CS0246: The type or namespace name `Interface' could not be found. Are you missing an assembly reference?