You will have to obtain a SCSI controller card, and, depending on features, you're probably looking at $50-100 on the low-end of things, and you can shoot past $1,000 for the high-end, server-class stuff.
I suspect they're all 68-pin drives, so you'll need a card that supports them.
It's not the newest thing out there, but for starters, the
Tekram DC-390U2B or DC-390U2W (has a few more features) are pretty good, and use regular PCI slots (not PCI-X slots found on server boards).
You will also need a terminator, which may or may not be included with your SCSI card.
You need a terminator because the SCSI card acts like a bus for the SCSI drives and needs termination after the last device on the chain.
You will need a cable with 5 or 6 connectors: 1 to connect to the SCSI adapter, 3-4 to connect to the drives, and the last one in place after the last drive in the chain.
Depending on if you get the parts new, this could run you between $50-100.
There's other SCSI cards out there, but the Tekram ones I've suggested are fairly inexpensive, especially considering they're SCSI.
Now, if you're got 80-pin drives, know that those are for hot-swap setups in servers. I don't know if there are any adapters to 68-pin or the older 50-pin SCSI connectors.