If the display uses ADC (Apple Display Connector)
it won't have a power adapter or plug, but you will need a DVI to ADC adapter
and a Mini DisplayPort to DVI adapter.
This is the series of Cinema displays I want to purchase :
It says it does not come with an A/C Adapter. I have an 2010 iMac. Can I still use it or what will I need to use it?
It needs the power supply.
If you can't find the 23" version, you could use the 30" power supply: