1996 Chevy Astro high pitch sound when we first start the c

it could also be a worn belt, to find the power steering resevoir, look on the left side of the engine, (when standing in front of it) and find the belt, at the highest point of the belt is a pulley that should be the powersteering pulley, just above the pulley should be a small black box shaped resevoir with a cap on it, that should say ,"power steering fluid". see if you find it and let me know first before you put anything in.