Can some tell me what size cake will a recipe of MMF cover? I would like to do a 10 inch with three layers.Thanks

Here's a chart that will help you:

http://www.earlenescakes.com/Fondantchart.html

I made 3 batches of MMF a few weeks ago for a wedding and I weighed them all after I was done. 1=3.2lbs 2=3.14lbs 3=3.4lbs

I used a batch and a 1/2 to cover a 10x10x4, 8x8x4, and 6x6x4 square cakes. Though, I should have used that other half batch and made the fondant covering on my 6" cake significantly thicker and just slightly thicker on the 8" cake.

A little off from the chart above, but it's a good estimate.