劫掠 is formal/literary, used for war, piracy, and large-scale historical looting. For everyday robbery, use
抢劫 (qiǎngjié). For sweeping a museum or archaeological site,
劫掠 is the classic word — common in news about WWII Nazi looting (
纳粹劫掠) and the 1860 Anglo-French sacking of the Old Summer Palace (
英法联军劫掠圆明园).