The human heart is comprised of four chambers, of which two -- the left ventricle and the right ventricle -- intake low pressure blood and outflow high pressure blood. The process of taking in a low pressure fluid at a given volume, and then sending out the same volume at a higher pressure, is "pumping". According to this logic, the heart contains *two* ventricular pumps, which use muscular contraction to raise the pressure of the blood.
At a little more detail, the left ventricle pump sends high(er) pressure, oxygenated blood throughout the body -- brain, digestive system, limbs, etc. -- through the arterial circulation (arteries). The right ventricle pumps blood which has returned to the heart through the venous system (veins), which is depleted of oxygen, out to the lungs through the pulmonary circulation (this circulation is distinct from the body circulation in that the artery carries low-oxygen blood and the vein carries high oxygen blood). After oxygenation, the blood is returned to the heart through the pulmonary vein, making its way to the left ventricle and the arterial circulation to repeat the cycle.
blah blah blah.... the left and right ventricles are the pumps so the answer is two