As for Windows XP, you can probably find them on ebay. It's on old operating system that is no longer sold and Microsoft has stopped supporting it which means they have stopped releasing security updates for it.
The manual for the laptop is available at support.dell.com. If it has an entact coa sticker with a legible product key you can usually buy an os disc on ebay. If the coa sticker is unreadable or missing you will need to purchase a new OS with license.
As for Windows XP, you can probably find them on ebay. It's on old operating system that is no longer sold and Microsoft has stopped supporting it which means they have stopped releasing security updates for it.