If you have submitted a request to obtain/extend a residence permit to the questura (police), then there is a convenient service to check its status: https://questure.poliziadistato.it/stranieri/?mime=1&lang=polish&pratica=
The service is presented in many languages.
Case number or also called 'Numero Assicurato' is the number that is indicated in a field Password, issued be Italian post at the time of documents submission at the post office.
