In Illinois, every civil court case is filed with a unique docket number. Your cases's docket number will be written on every court order you receive.
Additionally, each time you file a notice of motion, you will have to include the docket number for the case. For family law cases (Domestic Relations cases), every docket number will contain the year the case started, followed by a "D".
For example, if the case started in 2020, the docket number would be:
"2020DXXXXXX", where the X's are different numbers for every civil court case that started in 2020.
If the documents you received for your case do not contain a docket number, it may be an administrative case number.