Here is a site from the UK with great explanations and pictures of the most common worms chickens can get. https://www.flytesofancy.co.uk/blogs/information-centre/poultry-worms-treat-prevent
That doesn't look like worms. There are several kinds of worms that can inflict chickens and none look like that. Maybe it's more a cecal poop? Have they shown any symptoms at all?