You will need to purchase the program in order to get a serial number for it. Because it is an 11 year old program, you will need to buy a used copy on Amazon or eBay. Adobe will not provide you with a serial number for a product this old.
Aren't there features that will not be able to be activated on version 3?
Good point, Bob! That's another potential challenge with working with obsolete software. You won't get any support if things don't work.