I link the monitor and the pc?

Also thank you so much for your help really appreciate

The first option sound nice but the box is long gone. To be honest I'm just trying to have a desktop monitor. Yesterday I plugged the hdmi cord to my brother's laptop but perhaps I did something wrong because the screens where mimicking each other down to the mouse movement. The big decision for me is money. And that's exactly what I'm trying to spend 50-100 - something very affordable. There's a pc box that I was looking on Amazon that is around $80 except I'm not even sure if that would work correctly with my monitor. (I can't find it right know)

It came with a hdmi cord and we tried to hook it up to an old 2000s pc but it didn't have the hdmi plug

Okay so I don't know much about monitor but I bought it for school work and movies. But it keeps saying no video input/output so I'm not sure what to do?

Any affordable Recommendations for pc??