How do I connect a laptop to my newer Mac monitor?

IF you are attempting to use Target Display Mode please read Target Display Mode and you will see you are very likely out of luck. Please remember Macs are computers, they are not external displays for other devices. However, there are third party solutions you can try.If I were in your shoes, I would simply buy an external display for your laptop. You will find it:

• Less expensive as no expensive cables and software are needed.

• MUCH more reliable.

• Extremely simply to setup and maintain.

You have two options:

Use the USB-C port of the laptop to connect to the monitor (which I assume is USB-C/Thunderbolt) or find the rare HDMI to USB-C adapter.

I only found one from CDW:

https://www.cdw.com/product/siig-hdmi-to-usb-c-port-4k-60hz-converter-adapter-adapter-hdmi-usb/6329704?pfm=srh

What “newer Mac monitor”, exactly?

No you can not use a 24" M1 iMac (if that's what you have) as a monitor for a laptop or another computer.

They say they have a monitor, not another Mac.

He actually said a "Mac Monitor" that lead me to believe he meant an iMac.