If your lawn has an uneven cut after using your John Deere push lawn mower you may have a bent or dull blade. Make sure the blade is secured tightly to the lawn mower. If the blade is bent it will need to be replaced, if it is dull then you can either sharpen it or replace it.
You should also check the wheels to make sure they are all at the correct height. The two front wheels should be at the same height as each other and the two rear wheels should be the same height as each other too. Usually the rear wheels are set a little bit higher than the front wheels to give the best cut.
You can find the model and serial numbers located on your John Deere push or self-propelled lawnmower on the left side of the mower deck.
NOTE: if you need a part for the small engine in your John Deere push or self-propelled lawnmower, there will be a separate model/serial number for the engine. Here are the small engines that are available in your John Deere push or self-propelled mower. Visit the page of the engine you have to find out where the model/serial number is located for your small engine model: