Mechanical MS Mouse on iMac?

I'm using an optical mouse for the first time on my new iMac (Apple MIghy Mouse) and for me it just sucks*. I'd very much like to try my old mechanical Microsoft wheel mouse. From the net I see I will need either a PS2 to USB adaptor or a PS@ to USB converter.

Which is it?

Will the iMac accept it?

* I don't like the response and it aggravates an old wrist injury. The Ms mouse doesn't; so its no small thing.

I phoned Mac they said the ps2 will work with and adapter.