i have just got a puppy dog and this morning when it had a poo they was a long worm that came out is this normal after a worming tablet i don't know if he has had a tablet if i gave him another would it harm him he's 8 weeks old thanks

With the modern wormers you rarely see any worms as they are killed at the larval stage.  to see mature worms he was either carrying a ehavy burden or was worme4d using an older preparation like Piperazine.

Ring his breeder to check when he was last wormed, and if just doen do him with a modern wormer like Panacur when he is next due.