Look for a sequence of three (or four) jumpers with labels like A0 A1 A2. Those are the scsi address selection jumpers. The presence of a jumper is interpreted as a '1' and the absence of a jumper as a '0'. A2 is the most-significant bit. A '100' is therefore scsi address 4. Sometimes, the connector for the external scsi ID selector has been removed, so you have to set the ID by configuring jumpers on the drive itself.

Termination requires that something supply its power. The drive allows you to specify whether that power comes from the host computer, or from the local power supply within the external drive's enclosure. The corresponding jumper will be labeled either TE or TP (I don't remember which). Try putting a jumper on one or both. Permute until goodness occurs.