Check the internet sources of instrumentation providers, like NationalInstruments. Usually drivers for stuff like this are included in driver collections for software like LabVIEW (which firstly was developed for the Macintosh). Do not expect an instrument connected to your computer to appear on the desktop by some magic - it will be accessible only using appropriate data acquisition software in combination with a working driver for the GPIB adapter.

Alternatively you might communicate to the instrument using a RS232 port (if available). You could use a terminal programme or HyperCard (with some extension in the stack ressources).