The negative formal command of "organizar" is the following:
No organice.
Formal commands are used when you talk to a person you do not know well, an older person or a person to whom you want to show respect.
When you use formal commands, you have to use the third person, both singular and plural form, and the present subjunctive. In this case, you use the third person singular form of "organizar".
If it is a negative formal command, you should also add the negative word: "no".