Is the robe worn under or over the belt?
If it’s worn under the belt, it’s a kaftan.
If it’s worn over the belt, are the sleeves short, full-length and loose, or as long as the garment and hanging behind?
If the sleeves are short, the robe is an overcoat with no identified name, the Short-Sleeved Full-Length Overcoat.
If the sleeves are full-length and loose, the robe is a ferace.
If the sleeves hang behind, the robe is one of the varieties of overcoats with hanging sleeves.