Where to find main shut off switch for breaker
You may have what is called a Rule of Six setup. This means that more than one, but no more than six, separate switches need to be turned off to turn off all power to the building. As I understand it, this was allowed many years ago in order to make large panels without having a really big main breaker, but it has been used in many different ways. It is not the normal way to do things today - I'm not sure if it is even allowed for new installations, but old "rule of six" installations that are functioning OK are grandfathered.

For example, in my house there are two pairs of fuse blocks to be pulled out in each of two fuse panels that came with the house (or at least have been there for a very long time) plus a main breaker in a subpanel added with my kitchen remodel, for a total of 5 items to be pulled or switched to cut off everything. If/when I finally get this all replaced with one nice big breaker panel, I will need to have the electric company pull the meter/cut power to do that. Of course, I'll want them to increase my total service at the same time, and the end result is a lot of work and money and..."someday".