What is the scale factor of a model car if the scale is 1 Inch=2 feet

To answer this question, you need to know how 1 inch compares to 1 foot, and in order to do that you need to convert these values to the same unit of measurement. You could convert them both to feet or to inches. Let's do inches since converting them both to feet would make the measurement of 1 inch a fraction (1/12 of a foot).

There are 12 inches in one foot, so your comparison is:

1 inch - 12 inches

This means that every foot you see in the object you are drawing can be represented on paper by a measurement of 1 inch.

If, for example a window measures 3 feet across, my drawing would be scaled down in my drawing in which my window measures 3 inches wide.

This keeps what you draw proportional to what you see.