No versions or URL given, but from that little image it seems you are using a commercial template/overrides.
Main setting in default templates for "grid/list" layout is in VM Configuration/Templates/Template and Layouts - Sublayouts for products in category. Default sublayout gives a grid, products_horizon sublayout gives a form of list, products_slim gives a compacted grid. But your layouts may be compeletly different if you have subcategory overrides.