Can I use my laptop display for my Desktop?
A laptop's screen lacks the ports that a typical monitor uses to receive input from a desktop computer because they were never meant to function as a stand-alone device. As a consequence of this fact, it is not possible to plug a desktop computer to laptop and use its screen as the display.
Are there workarounds?
If you have both your desktop and laptop connected to a network, along with the proper permissions, you may use a windows feature known as Remote Desktop Connection to control and display the desktop's content on a laptop computer.
Laptop no longer in use
If you have a good understanding of electronics, ample spare time, and no longer need an old laptop, you may manually solder a connection from the desktop to the laptop. Though there are YouTube instructional videos on the subject, it is a delicate, technical process and therefore not recommended as a common solution.