It’s not always quite that simple. The loop is specific to the model of sensor and how you are using it.
Generally most sensors use loop 1.
Some sensors have multiple functions, for example the Honeywell 5816 wireless door sensor has a wired input and the built in magnetic reed switch. If you are using the wired input it is Loop 1. If you are using the built in reed switch, Loop 2.
Always go by the sensor manual to set the right Loop.
I can help with specific instructions with the model numbers of the sensors, although all of the Glass Break, Smoke Detector, Heat Detector, and Motions I am aware of use Loop 1 for their primary function.
Some smoke detectors have built in heat detector or freeze detection circuits as well which use additional loops and are learned in individually.
What are the model numbers of the sensors you are using?