Question

how horse pool a cart explain with 3rd laws of Newton

Answer 1

when horse is pulls a cart then the horse pushes the ground (action ) and again ground gives the horse an opposite force to move forward (reaction )

Answer 2

The horse exerts a force in backward direction by his feet on ground, then the equal magnitude of force is exerted by the ground on the horse and when this reaction force is greater than the force of friction, the horse along with the cart move.