The card you have would almost certainly have been used with an Apple Portrait Display. Now, you could try to find one of them, with the cable to connect also being needed. They are fabulous monitors, and you could scarcely beat one for the authentic period look.

Alternatively, put out a feeler locally on kijiji for what you need, or pm me about a basic Nubus video card and VGA adapter package — Nubus Ethernet available too, should you want it.

Not sure whether that adapter linked from Amazonia would actually work with what you already have, but maybe. It is, however, a trifle expensive for a shot in the dark.