The post is a cylinder. Area of the surface of a cylinder is the diameter multiplied by "pi' (3.417) times the height (convert it to inches). So:
9" x 3.417 x 120" = 3,398.76 square inches.
We will round that off to 3,400 square inches. Each tile is 18.0625 square inches (4.25" x 4.25" ).
Dividing that number into 3,400 gives you 188 tiles. I would get 10% more or at least 210 to account for breakage and mis-cuts.
Easier way to picture this: Imagine your column is a cardboard tube and you slice it along one side and lay it out flat. It will be 10' long and about 2.36' wide. That means it is 23.6 square feet. The tiles are close to 4" x 4" which means that 9 of them laid out in 3 rows of 3 will make a square foot. Multiple 23.6 square feet (column surface area) times 9 tiles per square foot and you get 212 tiles, slightly more than the math calculation (because we used the actual size of the tiles which are a little larger than 4' x 4")
One question, unless these tiles are flexible (like soft material or are made up of smaller tessera tiles on a flexible cloth backing) they are not likely to be able to wrap around the curvature of a 9" pole.
It would take 173 dozen of them.
