I posted the following on the Google+ group
comp.soft-sys.math.mathematica and had no luck with responses. I've done a Google search and, to the best of my ability, used the documentation center.
The post I made was as follows:
I continue to receive "Unable to interpret unit specification m/s" (for example, but almost anything I attempt returns this message) with input: UnitConvert[55 mi/h,"m/s"] or UnitConvert[55 mi/h,m/s] or any other combination of quotes, omitted quotes, etc. Even the prediction/suggestion box, when I execute Quantity[55,"mi/hour"}, after it returns 55 mi/h, if I type in any combination of m/s, "m"/"s", "m/s", etc. into the box that opens when I select "Convert" in the prediction box yields the same "unable to interpret unit specification.
What am I missing? (As you may gather, I'm a Mathematica novice.)