just multiply the numbers together
1unitsx1units = 1units2
another example would be..
2unitsx2units = 4units2
cubic feet
It is a unit rate.
A unit rate is a ratio in which the numerator or denominator is 1 unit.
It is 1 square unit.
It is 1 square unit.
You can't convert that. Square centimeters is a unit of AREA (2 dimensions), liter is a unit of VOLUME (3 dimensions).
A unit of area or as of farmland is called an acre.
Magnitude
It wouldn't be called girth; instead, it would be called dimensions of a box. To find the dimensions, measure length x width. To know the area of the sides of a box, it would be length x width x depth (how tall it is).
You can't just convert any unit to any other unit. The units must be of a compatible type. Thus, you can convert a unit of length to another unit of length, a unit of area to another unit of area, or a unit of volume to another unit of volume.
Frequency has the dimensions of reciprocal time. The unit is "per second" also called "Hertz".
Yes. A meter is a unit of length (1 dimension), a square meter is a unit of area (2 dimensions).