Starter not working

Already had the battery tested its good. Someone told me its probably the voltage regulator, so I bought one and I cant figure out where it goes. Autozones website says on the center of the firewall but i dont see anything even close to what it looks like there

Hi:

To the best of my knowledge, the alt is regulated through the computer on the 1990 dakotas. Call a dealership to confirm.

Regardless, when you put the new battery in the vehicle, would it start or did you need to jump start it?

Let me know so I can better help you.

Joe