Pick a value for one of the dimensions. Divide 214 square feet by that value to get the other dimension. There exists an infinite number of possibilities. Example Suppose one dimension is 10 ft. The other will be (214 ft^2)/(10 ft) = 21.4 ft. The room could be 10 ft by 21.4 ft.
The short answer is "measure it."
The short answer is "measure it."