Welcome Eileen!
We need to know what computer model and sub-model you have, and its operating system to start to help. Think of this forum as an auto mechanic. If you call a mechanic and say, "My car is running rough," the first thing he'll ask is make, model, and year of your car. Same here.
If you can't figure out the model/submodel, you can enter the serial number in this apple support page:
https://selfsolve.apple.com/agreementWarrantyDynamic.do
and it will translate the number to a model/submodel. Report what it finds but do NOT post your serial number in an open forum. It is possible that the computer is too old or Apple's lookup function. If the Apple page reports it can't find your model, use this web site instead:
http://www.everymac.com/ultimate-mac-lookup/
By the way, this forum is for Mac hardware made before 1998; I suspect your computer isn't that old, so we will need to get you moved to a more active forum. This one gets little traffic and your question won't get the attention it deserve here unless your computer is really a pre-1998 model.
Allan from Idaho