I paid insurance in Kunshan for several months, but I don't know the social security number.

Whether you go to a pharmacy to register or go to the social security bureau, you must have your own social security card. If your old company pays you every month, the salary slip says that your social security fee has been deducted. Go back to your old company and ask the person in charge of social security. Because every company has new employees or leaves their jobs, they have to go to the Social Security Bureau to fill out a personnel increase or decrease form, and then copy the social security details of the unit for the month with a USB flash drive.