You will need to cut 9 1/2 blocks to finish up 9 inches.
You can cut 4 blocks across the width of the fabric.
You will need to purchase 1/3 yd of each fabric in order to get the 9 1/2 inch heighth.
However, with 6 fabrics, that will give you 4x6 blocks for a total of 24 blocks. You still need one more block. Do you have a 9 1/2 inch block from your stash that you can use? Or perhaps a white block in the center with an applique, or a block from the backing fabric.