Do you have a SCSI cable for your scanner (external, DB25 male to DB25 male)? If so, and you don't currently have plans to use other SCSI devices, then you shouldn't need an adapter at all. The 1230 SCSI cable and the scanner cable should connect just fine. :-) External SCSI devices are generally always 25-pin, while the pin count for internal devices vary (50, 68, 80 ?, etc.). Just make sure termination is enabled on the scanner. I own a UMax scanner myself (a hulking 1200S) and recall that some UMax scanners do poor internal termination...but for just one device on a short cable, this shouldn't make a difference.
If you eventually decide to add internal devices, you'd want the 25-50-25 adapter from Power Computing. Until I saw your link, I had no idea such things actually existed! I made my own adapter a number of years ago and it was a hellish experience, but it did work on the first try. It's currently powering a Seagate hard drive, a Plextor 40x CD-ROM, a Plextor Premium CD/RW (via an IDE to SCSI adapter), a 250MB Zip, and the UMax, and it all works very well. It annoys me that Phase5 or DCE never put a 50-pin connector on the 1230 SCSI (since it's much easier to go from 50->25 than the other way around), but it is a useful little board.
Hope that helps,
Todd
