You need to know the make and model of the card in order to find the drivers.
If you don't know that information, download, install and run
Belarc. It may be able to identify the card.
If it can't identify the card, you may be able to find what you need by removing the card (with the computer shut down) and looking for a make and model number on it.
Once you have the make and model, go to the card manufacturer's site to find the drivers or post the information back here.