Why would my 1994 chevy cavalier rs not get oil to the engine even if i replaced the oil pump?

it's possible that when you put the oil pan back on, the pickup tube for the pump got moved, and isn't down in the oil anymore.

What engine do you have. If it is a 3.1 you may have issues with the oil pump driveshaft or drive gear off of the cam. If you have the four cylinder let me know I will have to check. If it is the V-6 the pull the pan and check the oil pick up as Madmopar suggested. If there is an issue fix it. But since the old pump and new pump don't work it must be something else. While you are in there un-bolt the pump the driveshaft should fall out. Check it for damage. If it looks good put the oil pump end on a screwdriver and tape it. Stick the shaft back into the hole and try to turn the drive gear. It is driven by the cam and should only have a couple thousands of play if it turns you will need to pull it which means removing the top half of the intake manifold. Here is a pic of the 3.1 so that you can see the parts in question.

423 for the driveshaft 432 for the drive gear