If you want to find out how much a certain stock was trading for on a certain day in history, perhaps to calculate how much it's grown since then, you need some historical prices.
Fortunately, they're generally easy to find these days, thanks to the Internet, although even without a computer you may succeed simply by calling the company in question and asking its investor relations department. Another good resource is your public library, where librarians should be able to help you look up the price in newspaper archives or elsewhere.
Still, the easiest resource is your trusty computer. Click over to The Motley Fool's Quotes & Data area, type in the company's ticker symbol, and click "Go." On the page of information you receive, look for a small link called "Historical," and click that. From there, you can specify exactly the info you'd like to get.