The pack gvterm, IIRC will generate a dot file. A dot file is an input specification for GraphViz.
I take that you have never used GraphViz? If not you will need to install GraphViz and then run the GraphViz dot command to convert the dot file into an output format such as SVG, PNG, PDF, etc.
There is some example code of doing this in Convert facts to GraphViz dot file using DCGs, specifically
SET PATH="C:\Program Files (x86)\Graphviz2.38\bin"
dot -Tsvg module_graph.dot -o module_graph.svg
HTH