i need it for about 60 people

sugar 5lb 15oz
flour 3lb 6oz
cocoa powder 1lb
baking powder 1/2oz
baking soda 1/2oz
salt 1oz
eggs 12
milk 6 cups
oil 3 cups
vanilla 6 oz
water 6 cups

please help!
thank you

You do know that you are asking someone to do a lot of work for you. And frankly you should try and research how to do this yourself if you are going to be in the cake business. This is asking a lot of someone.

What size cake pans does that fill? How many cups of batter does it make?

From there you figure out what size cake you need to make to feed 60 people.
http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm

I don't know the science behind scratch baking and reducing recipes. But if you know you only need a 1/3rd or a 1/2 of the recipe, then you can just do the math to figure it out.