Each formal letter has a solid structure.
You start by mentioning your name, your address, and birth date. It is usually written in the left top corner like that
1665 Adams Mill Road
Marietta, GA 30078
September 12, 1999
Next paragraph is written in the same form, but you name the person you write your letter to.
Appeal to the person with the standard phrase. Choose one of these two
Dear Sir/Madam (if you don’t know the name), or
Dear Mr./Mrs. Name
Then goes the first paragraph, where you specify your request.
I am writing to you …
In the second paragraph provide your reader with the reason for your request.
The third paragraph is optional. It can be written if your case has some sort of urgency or deadline.
Finish your letter with the following sentences.
Thank you in advance for your assistance. In case of any questions, please contact me at your best convenience.
Do not try to come up with a perfect letter. The best thing you can do here is to follow the standard form and be precise in your request.
It won’t hurt if you contact your administration and ask about the form of the letter. They might have some specific requests there. If not, follow the given structure, it is pretty universal.