Assets/Editor/CopyMoodBox.cs(7,12): error CS0246: The type or namespace name `MoodBoxData’ could not be found. Are you missing a using directive or an assembly reference?
This is a compilation error indicating that your project is missing a file describing the type MoodBoxData.
The filename is probably MoodBoxData.cs as it is good practice (and required most of the time) to match type and filename. Sometimes a class containing data (i.e. only variables and no or very few methods) is defined in the same file as the class using it (could be MoodBox.cs is your case).
Without more information about your problem, I cannot help you further.
Make sure you have
using System.Collections;
At the top of your script