How can a parallelogram be cut and rearranged to show that the area of a parallelogram can be calculated using "a=bh", the same formula used when calculating the area of a rectangle?

I have attached an image that hopefully will be helpful for you.
Step 1: draw a line from one of the vertices so it intersects the opposite side at a right angle (this is called the height). you have just divided the parallelogram into a triangle and a trapezoid.
Step 2: place the triangle you created over on the right side of the newly created trapezoid. this will create a rectangle, whose length is the same as the base of the parallelogram, and whose width is the height of the parallelogram.
hope this helps.