I assume it has a freezer on the top and fridge on the bottom?
If your freezer is cold but the fridge is luke warm, it is most likely the evaporator fan in the back of the freezer. That fan blows the cold air from the freezer to the fridge compartment.
I have a Whirlpool and the evaporator fan started intermittently spinning and the freezer would get into the 50's. That happened at about 18 months. I got a replacement on Amazon for about $20 (probably more now with inflation). I also bought a second one to cary as a spare. Its about a 15-minute job to replace it.
The motors are cheap Chinese junk. If you can't hear the fan running, that's probably your problem.
To check it there should be crews holding on a plastic shroud on the back of the freezer that covers the evaporator coils. You'll probably have to remove some beauty caps to access the head of the screws.
Once you have it off turn the thermostat to max cold, close the fridge door and see if the fan is spinning.... or just listen for the fan after cranking down the thermostat.
__________________
|