It is paramount in calculations to keep the units straight. This is a trivial example, but when dealing with non-dimensional numbers, such as Reynolds or Froude numbers, it is important that all units cancel. Moreover, there are constants, like viscosity, where the units are not intuitive, and complex calculations, such that the end result is, say velocity. It is a simple operation that is of great value to keep you out of trouble.
Nothing is left but m in the numerator or the final units left is m.
Our final and complete answer to the problem is 0.3048 m. Lets say, we mess up our conversion from ft to m. We were in a rush to get it done and we start with the equation, We calculate the equation numerically, resulting in, No, problem, we know that a foot is much smaller than a meter. But we check ourselves, anyway using the units. We know something is wrong and we should go back and check.