I have yellow jacets in the ground I can't mow how can I get rid of them?

I would hire it out. Pay somebody who will have the proper equipment, methods, and experience to not get stung. Some local govts offer a vector control service.

Otherwise... yellowjackets return to their nest at night, and become more susceptible to control. There are aerosol insecticides designed just for wasps and yellowjackets. These insecticides shoot a stream so that you can stand back from the nest entrance hole. Get the product that provides a quick knock down . Either, wear gloves and a bee veil for safety or be prepared to run.

UCIPM