They're on your Win98 CD already. You just have to tell Windows where to find them. You must have an original CD to do this, not a manufacturer's "system restore" disc. Here's how:

If the card still auto-detects, simply point it to the directory on the Win98 /ME cdrom: \drivers\storage\advansys\ and it should find everything correctly.

If it has already tried to install and is not asking again, go to the control panel (Start Menu - Settings - Control Panel) under Add New Hardware.
Go through the menus, no automatic searching, and go to where you pick the type of your new device. Go to SCSI controllers. Pick Have Disk, and Browse to your Win98 / ME cdrom. Go to directory Drivers, Storage, Advansys, and hit OK. The driver should appear in a list and install from there.