In most places a felon can own a gun after 10 years.
That means that if you're a felon and have not been arrested or convicted of any other crimes within those 10 years then you can usually own a gun after that time.
You would have to check with your local laws to be sure though.
Because some states it can be different but in most states felons can own a gun 10 years after they have been released from prison and 10 years after they have been convicted as a felon.
However if you were arrested again during those 10 years then the clock resets and then you won't be able to own a gun for another 10 years.
So if you're a convicted felon then you must be sure to stay out of trouble if you want to own a gun 10 years later.