Hello, 
The cake recipe called for 9" and 2" height  pan but I want to make 7" or 6" or 4" inch cake.  How would I do that? 

And

The cake recipe called for 9" and 2" height  pan but I want to make 6 with 3" height?

Thank you!

The recipe calls for that size pan because the amount of batter that the recipe makes is enough for two 9" pans.  If you want to make smaller size cakes you just need smaller pans (or bake a 9" and then cut it down to a smaller round).  For 2" deep pans you fill them about 2/3 full.  For 3" pans you fill them about 1/2 full regardless of how large or small the pan is.

thank you!!!!

One can use *ANY* size and shaped pan as long as there is enough batter for it/them.   That recipe you mention could be  used in an 11x8/ 9x13 (sheet) pan along with many others.

Thank you!