The human pancreas contains exocrine acinus cells (simple cuboidal epithelium) and Islets of Langerhans. Despite looking online I cannot identify what type of epithelium the Islets of Langerhans conform to (e.g., cuboidal, columnar, squamous). I'm confident it is not squamous due to the shape of the cells, but the distinction between cuboidal and columnar seems equivocal here.
I think the image you've attached lacks clarity. If you see the image below, you could say that the epithelium is cuboidal with central rounded nucleus.
Unlike the oval nuclei of columnar epithelium, rounded nucleus suggests that they are cuboidal in shape.
The image is from https://webpath.med.utah.edu/HISTHTML/NORMAL/NORM010.html