If it takes a 8.5 x 8.5 inch square to make a 2x2 inch finished *window* if that is what you said... then a yard would make approximately 20 of those 2x2 inch windows. About two yards to make one square foot of windows.
100x100 is just over 8x8 feet... 64 square feet ... that would be 64 x 2 yards?
I.E. *Just how big is your bolt of muslin ..... or how many bolts do you have ?