Agree with joanna73 ... there is no law dictating how much notice employers can "require" when you separate from your job. However, unless you live in a state where state law dictates otherwise, you may need to meet the employer's policy requirements in order to retain benefits such as eligibility for rehire and payment for vacation/sick/PTO time accrued up until your last day of employment.
OP -- your employer has a human resources policy manual, whether in a binder or online on the facility's intranet. Find it. It will have all the info you need on the procedure to follow to separate from your job.