There may or may not be a specifically labeled breaker.
Some have it that way, but our sump activates when we turn on a "Main Battery" breaker on the DC panel... along with some other minor loads like the CO detectors, etc.
You may have a fuse panel, too, perhaps blade fuses
, for small loads like that.
And then if your sump is a commercial
box, it's likely got a float switch inside to activate the pump when water
reaches a certain level. If the float switch isn't working, no pumpee.