Hi, and welcome.
I'm guessing you mean that the cobs are 10in. long? Ten inch kernels would be really amazing. Sometimes you can tell if the kernels are formed inside by just feeling the cob. If it feels full and firm and a little bumpy, things should be good.
Otherwise, as it's getting pretty late in the season, I'd simply harvest one and see if you have edible corn in there or not. Something might have been eating the silk off the ends, or it may be a variety with very short silk. But the silk is the 'tube' that pollinates the kernels so not sure what you'll find until you unwrap one.
Maybe you could take a peek, by tearing a small opening in the husk at the tip (go for the fattest cob) to see if there are good kernels in there. If they are not mature yet, you can close up the tear with a piece of sticky tape.
