How do I leave an abusive relationship with kids, while he is in jail?

Do you have any friends or family that could help you? There are countless of organizations that are dedicated to helping women in need (but it does depend on where you're from so there's no org i can recommend you rn). How long is he going to be in jail for? Does he have other connections outside than you and your kids? I would maybe seek legal advice from a lawyer and make sure you have sole custody over your kids (which should be easy considering he's in jail).