That's a single pole GFCI breaker. If it was a 2-pole there would be another terminal for the neutral. Should have looked at the old GFCI, it would say whether it is 120V or 240V, but you should be able to determine that from the wiring. Looks like someone just yanked wires out without seeing what/how they were landed.
First thing I do on a panel change is find all the white wires on the breakers or fuses, then mark them to identify them as hot/ungrounded conductors. Then check for MWBC and tape them together and mark the neutral for them. Also check for any color besides white or green on the neutral bar. If I find another color, I tape it white or green to identify it as either an EGC or neutral.
