Wow, Shelia, your post raises lots of questions -

What is the model number of your mower? Are you saying that you have adjusted it to the highest setting, and that it's still mowing the grass too short? Or are you saying that something is preventing you from putting it on the highest setting? If yours is a riding mower or lawn tractor, are the tires properly inflated? Have you somehow damaged the deck by running into something? Have you done any work (like installing new blades) that might have caused the problem? We really need a better picture of the problem in order to suggest solutions.

Maybe the ground is just very high there...

It is a riding lawn mower. It is an old mower that I found
in my dad's garage. I put in a new battery and I'm using it to mow the yard. I inflated the tires to the correct amount of air. Thanks for trying to solve my problem.

Look all over the mower for a handle that raises or lowers the mowing deck. It should be readily visible.
I f you would tell us the name/make of the rider, Horse power, and other pertinent facts, we should be able to help you! The serial number plate, or sticker should be under the seat. Post everything on that sticker! it will help us to help you. by: Rusty Jones, who has had a lot of Sears/ Craftsman lawn riders to fix. RJ