Controls do not have a "hidden" property (no objects in Access have a hidden property). They do have a .Visible property.
For future reference, I suggest you familiarize yourself with the Object Browser in the VBE -- open the VBE and hit F2. You can then restrict your search to the individual libraries used in your project. It does take a while to get to the point where you understand the object model, though.
Also, you can rely on Intellisense to learn the properties/methods of an object, so in the code of the form you're working with, you can type "Me.MyTextBox." and the Intellisense dropdown will show you all the properties and methods of that particular control. It doesn't work for a generic control variable (as in your code) because different control types have different properties.
And, of course, the properties sheet gives the names of the properties, even though in code they don't always use the same orthography (usually they are the same with spaces removed).
Also, there are differences in how you might want to do this depending on whether it's a regular form or a datasheet form. In a datasheet, your controls also have .ColumnHidden and .ColumnWidth properties (setting those in any view other than datasheet view has no effect, and neither of those properties are available in the standard property sheet, but changes to them are retained when you save the form).