American style fridge freezer frozen on back wall of fridge

[2anddone]

Why would the fridge half of my American style fridge freezer be frozen on the back inside wall behind my salad drawer? Just walked into my kitchen to a puddle on the floor.
It's 15 years old is it dying??
All food inside is cold and the freezer side all food is frozen.
Please tell me there is a quick cheap (preferably free) fix!

Is the drain blocked?

I wouldn't even know where to find the drain!! 🤦‍♀️🤦‍♀️

Drain will be at the back of the fridge section, possibly just behind the top of the salad drawer. Is it full of gunk?

Poke a toothpick down the drain to unblock it. There should be a reservoir on the back of the fridge (behind the fridge not insid it) where water evaporates from. Check if that's full of water, mop it up if it is.