Well it's done differently in different parts of the world BUT here at least (simply)

1) Power points and light are separate circuits (i.e. breakers) always
2) Power is usually split into more than group however for a small townhouse like ours we have just two circuits which equates to opposite sides. A larger house might have a couple more, maybe 4 or 5..

So 3 out of a lot doesn't sound like a breaker to me but more like a break in the wiring elsewhere which I can only guess to be burnt out wiring (which would not be a good thing) as a result of a slight overload. I presume the 3 are all in fairly close proximity to each other?

Is this an old place i.e. the wiring may be suspect?

If it was only one, I'd suspect the physical power point. 3 (assuming they stopped working at the same time) tends to suggest upstream from the powerpoint.

There's really not that much too it for the actual wiring usually. The line, neutral and earth should all just run back to the circuit board via some junction boxes. Work your way back from there.

If you have a lot of breakers (i.e. the 3 might be on just one exclusive one) then perhaps it has burnt out. Slightly tedious but do you know that each breaker is actually switching something else on/off. i.e. turn them on/off individually and work out what each one does.