1992 Starter motor should have a built in starter relay/solenoid.
If you look at this picture:
The larger terminal at the top back of the "solenoid" connects DIRECTLY to the Battery +(positive) terminal.
The smaller terminal on the left back of "solenoid" is the "S" terminal of the internal starter relay, this connects to a smaller wire that goes to the Key Switch(ignition switch), when you turn the Key to START that sends 12volts to this terminal and starter relay/solenoid closes and battery power is sent from upper post to lower post(starter motor) in picture.
This is a generic picture not meant to be match to 3.0l starter motor.
Older vehicles used to have a separate Starter Relay on the fender well, and the "S" wire and Battery + cable connected to this relay, the solenoid on the starter motor was activated by this Relay.
This fender relay was often mistakenly called the starter solenoid.
A Solenoid is a device that causes physical motion when activated and deactivated, in a starter motor the solenoid pushes starter's gear out to turn flywheel then pulls it back in
A Relay is a device that passes electrical power or cuts power when activated or deactivated.
On newer vehicles the starter relay and solenoid are combined