|front of battery is what you want. It’s on the far left side of box - closest to fender wall. They normally don’t just partially fail - either it has a connection or some kind of short made it so hot it melted. Fusible link works the same as a fuse but uses a thicker gauge wire to accommodate higher cuurents (30-50 amps or more).
You can test the link with your meter using its lowest resistance setting. Pull the link and measure across the connection points. You should get a very low reading like 0.5 ohms.
Here’s a picture of the blue link: https://www.z1motorsports.com/relays/nissan/oem-blue-fusible-link-p-6954.html