where is the brak power booster located?

The master cylinder is bolted to the booster, . . . if you have one. While not common, some cars don't have power brakes. If you don't have power brakes, the master cylinder will be bolted right to the firewall.

You can have non boosted brakes (factory) that have had an in line booster that is not fitted to the master cylinder, the common factor will be a large vacuum line going to the booster unit and if it is remote mounted it will have a brake line going in and out as well, there will be no electrical connections on it.

They did make some of these with a hydro-boost instead of vacuum booster. If you have hydraulic lines going to it from the power steering pump, then you have hydro-boost.