If you live in the United States, you should use inches. If you live outside of the US, you should use centimetres.
Inches or centimeters.
meter
A foot.
Centimeters.
This cannot be answered since a linear foot is a measure of length while a square foot is a measure of area.
The ISO length unit to use would be the cementer.
Inches and feet measure length in standard units, in metric meters and centimeters measure length.
Yards or Foot.
There is no way to convert between feet (length) and square feet (area). A square foot is a measure of area while feet are a measure of distance. The two measure different things. To get square footage, you have to have a length in feet and a width in feet.
You can't just convert any unit into any other unit. The units must be compatible - measure the same type of thing. For example, you can convert a unit of length to another unit of length, or a unit of time to another unit of time. An atmosphere is a measure of pressure, a foot is a measure of length, so you can't convert it.
foot
There is no conversion factor. A foot is a unite of length, a square foot is a unit of area. The measure two different things.