It looks like Training_Image.Files is a cell array of chars, and you are attempting to take one of those chars and assign it to be a cell in a cell array (as opposed to assign it to be the contents of a cell in a cell array). You can do what I think you want to do in a couple of different ways:
files(h) = Training_Image.Files(n(h));
or
files{h} = Training_Image.Files{n(h)};
But then you're going to run into an error when h = 16 because n only has 15 elements.
