Before you start disassembling, look for these telltale signs that the pump is the culprit:
If your dishwasher is full of dirty water, you need to remove it before accessing the pump to avoid flooding your kitchen floor. how to unblock a dishwasher pump
Most dishwashers (Bosch, Whirlpool, Hotpoint, Samsung, etc.) have the pump behind a cover at the bottom, under the spray arm. Before you start disassembling, look for these telltale