As said, most PC monitors will have either 15 pin d-sub (VGA) or DVI, or both on them. 15 pin D-Sub (VGA) is the blue ended one and DVI is the white ended one;
From memory, the Iyama monitor has both, but it depends on what your PC has. Have a look, and if you have a white connector that looks like the one in the pic, then get yourself a female to female DVI lead. If you don't have that, you will have the blue VGA connector, so get yourself a female to female VGA lead.
Most, if not all, monitors will come with the basic VGA cable, many will come with a DVI cable aswell. Your old monitor is like my old one - has the cable built into the monitor so it just needs attaching to the PC.
If your mate bought himself a £30 lead, then he should still have the standard one it came with.
However, if it came from a "mate" (

) then he might only have the screen and thats it
Either way, you can get a cable from virtually any PC shop, or the likes of Curry's, Dixons, PC World etc for a few quid - no need to spend £30 IMO.... Less than a tenner will be fine