A statement of purpose is an academic essay that highlights the training and expertise that you will bring to your chosen program. Cut out any references that suggest failing or unsuccessful grades. Highlight your experiences as a special officer, note your specific skills and how they relate to nursing. Note and exploit your transferable skills - you have a ton of them. You need to sell your essay with confidence. Stating that you "had always done the minimum when I was working on my degree from the University of Michigan. I didn't enjoy most of the classes and I had no goal in mind, except graduating" doesn't fill me with confidence. Regardless if this is true, do not state it in your SOP rather, always suggest what you did achieve, not what you didn't.
Someone with your experience has a lot to give to any program. You should therefore exploit such knowledge.
Your last paragraph should state why you are choosing this specific program at that specific university.