Pin 1 of the sockets should have a square solder point.
I'd recommend using an external terminator (esp. an active one) - much easier if you connect external devices every once in a while.
On some A3ks the term power diode is reversed which pretty much disables proper termination, no matter if active or passive (it does work if the SCSI device supplies term power). While you're at it: check pin 25 of the external port for 5V (from the A3000 guide).
