what is meant by fine sugar? is that confectioners or granulated sugar?

Yes, as others have said, it is super fine or caster sugar, you can use granulated as suggested!

Yes, what Stephanie B. and Nancy both said—"fine" sugar refers to "superfine" or "caster" sugar. You can approximate it by blitzing up your granulated sugar a bit.

I think caster sugar, also called baker's sugar in the US, might be what they mean. Coincidentally, baker's sugar is one of the few types that happens to be in stock, as these finer crystals aren't as common in US baking.

Have a look at the attached article. I think it is zucchero semolato (very fine crystals).
Probably not confectioners' sugar, as that has cornstarch added.
Probably just buzz some regular granulated sugar in a blender or processor a few minutes to make it finer and add.
http://wordsofnona.com/2015/09/14/sugars_white_sugar/