You can’t do that in one line, the first line is a declaration of a variable called ArmorType of type “ArmorTypeEnum”, it will have a value of Light, Medium or Heavy. The second line is the definition of a enum, setting possible values for that enum and a type to group all the values.
I think you can’t do the private/public thing either, if you have a public variable of type ArmorTypeEnum you have to make the enum public so other scripts know what that type is.