Sole prop to LlC how do I file taxes?

Hi my questions is how to file taxes when switching from a Sole Prop to an LLC half way through the tax year. Do I file with both EINs?Or do I break it up from the old EIN to the new one and file 2 Schedule Cs? We also have 100 or so independent contractors do I send them 1099s with both EINs on it?