How many levels in campaign are there for call of duty 5:world at war?

i am trying to unlock zombie mode and am estimating how long it will take me.How many levels in campaign are there for call of duty 5:world at war?
there are 15 mission in solo in order to unlock the Nazi zombie mode. you have to complete all of those. But be warned if you have a Wii, DS, and a PS2, you not lucky to get one due to graphics problems.How many levels in campaign are there for call of duty 5:world at war?
For the wii there is 14 missions. But for the x box 360 and other systems i think there are more.