To find the perimeter of a shape I add all the measurements (length and width) together and make sure I add the unit of measurement to the number.
To find the area of a shape I multiply the length of the shape by the height of the shape e.g. length x height. I make sure I add the unit of measurement to the number.
Example: A rectangle is 6 cm by 9 cm
Perimeter - 6 cm + 6 cm + 9 cm + 9 cm = 30 cm
Area - 6 cm x 9 cm =54 cm squared