Kitchen tap faucet has an extension sprayer, that pipe is cut. I would like to replace this pipe.

Do you mean the hose between the faucet and the spayer handle? If so that hoes will unscrew from both the handle and the faucet, replacement is a hardware store item, nothing special. It will be difficult trying to unscrew the hose from the faucet, a basin wrench will come in handy. 11" Standard Basin Wrench