That Adaptec adapter is similar to the one that I linked in my previous post, in that it's designed to connect to an external SCSI peripheral having an HD-50 (High-Density 50) connection. Unfortunately, 50-pin SCSI-I/II hard drives have a male IDC-50 connection. Using an additional adapter like this
one and a 50-conductor SCSI ribbon cable, you could use the Adaptec adapter to connect the drive to a USB port. The conversion to USB only provides a data path, it doesn't provide the necessary 12 volts & 5 volts that power the hard drive via its molex power connection. This is why the drive really needs to be installed in an external (powered) enclosure. Of equal importance, is the need for a driver, so that the adapter is recognized by the system. If the manufacturer doesn't specify Mac compatibility, they won't have a Mac driver. The product info for the
adapter that I linked indicates that a Mac SCSI configuration utility (OS 10.2.7 ->) is included on CD. Even with this adapter, the hard drive needs to be installed in an external, powered enclosure having an HD-50 SCSI connection or one adapted to an HD-50 connection.