It sounds like your shop has single phase power, and then, the last guy got a 3-phase converter so he could run 3-phase tools.
And you have no interest in 3-phase tools.
Therefore, to you, the phase converter is of no interest whatsoever. You should completely ignore it, and simply wire all your single/split-phase tools to the panel in the way you are familiar.
If you are trying to be a little cheap, and reuse the 3-phase panelboard and wiring for single-phase tools, that is probably possible. Depending on the wiring of the phase converter, even with the converter off, 2 of the phases may be hot. That’s easy peasy, then; just use those 2 phases.
If it’s not that simple, then get us pix of the converter and wiring, and we can figure out how to carefully dismantle and remove the phase converter. You can take an axe to it if you really want to, but the thing is worth real money, so I’d dismantle it with an eye toward reuse or honest resale (so you can tell the Craigslist person “I carefully removed it complete and intact”, not “here’s a pile of parts that used to be a phase converter”).
Also, keep in mind, having 3-phase at your shop means you can buy tools at deep discount on Craigslist from all the pro-am homeowners who bought a 3-phase tool and thought getting 3-phase power would be easy.