I have a old desktop which doesn't have USB-c and a new laptop (have USB-C).

If I want to extend my laptop and desktop to 2 monitors, what device/hardware should I buy? Using the 2 monitor different time, example morning working using laptop, and night entertainment using desktop, but its very troublesome to plug in and out the hdmi/vga/etc.

So, anyone know which device/hardware I can buy for this problem?

2 monitor should be displaying different thing (Extend).