When you create some artwork and do a Save As, what output file format options do you have in your version of minicad? Also, are there any menu choices that say plot, rather than print?
The plotters used with Macs were many, because Microspot put together a broad package of drivers and plotter utility programs, and offered them in the MacPlot product as well as licensing a subset of the MacPlot functionality to various vendors. IIRC ClarisCAD and MacDrawII both use embedded Microspot software to do plotting to HP and Houston Instrument plotters. If a CAD program has an option to produce an HPGL format text file, something as simple as a terminal emulator can be used to dump the text to a serial port connected HPGL accepting plotter, which will hardware handshake to control the pace of HPGL instruction fetching in sync with the slow plotting operations.