To find the area of a parallelogram, you can use the formula:
\[ \text{Area} = \text{base} \times \text{height} \]
Given that the base is 12 inches and the height is 3 inches, you can calculate the area as follows:
\[ \text{Area} = 12 , \text{in} \times 3 , \text{in} = 36 , \text{sq. in.} \]
Therefore, the area of the sheet of construction paper that Miguel cut is 36 sq. in.