There'll be 2 connections to that alternator - a largish (typically) red wire fastened by a nut to the back, and a smaller plug (with 2 wires).
As stated, with the engine idling, the large wire should measure 13.5 - 14.2 volts to body or ground.
If the alternator output reads the same as the battery "plus" to body, and slowly decreases with time as the engine idles .. yeah, the alternator may be done.
Screw the box stores "what make and model sir/ma'am"! Look up "auto electric rebuilders" wherever you are. that old Delco with the core shouldn't run you more than $100.
The secret is not to say "bus" .. Just bring it in, plop it on the counter, and say "want one of these". Regardless of the eighty odd Delco alternator part numbers, there are only actually a few to fit any specific application. (The Delco stator housings clock on the mounting tab casting to account for multiple part numbers .. )
As well .. as you have a '97 without the electronics to care .. there are "one wire" replacement alternator options (they don't use the smaller plug) which work quite well.
Stranded in time.. Surrounded by evil.. Low on gas.