Walk Behind Lawn Mowers

I have a three year old AWD walk behind mower I purchased at Lowes. I Love it!! However, the wheels have worn down and are no longer aggressive enough to hold and my mower is now sliding on hills. Please, please, please tell me I can replace them?? (all four are all the same size and had a very aggressive tread when new)
Thank you in advance :)
Debbie Y