The first and second generation ID cards are different. I have two social security cards. How do I merge them?

If the number of the first-generation ID card is 15 digits and the number of the second-generation ID card is 18 digits, you only need to bring the original and copy of the ID card to the social security center for promotion and modification. If the content of the first-generation ID card number changes greatly when it is upgraded to the second-generation ID card number, it is necessary for the public security organ at the place of residence to issue a certificate to prove that the two numbers belong to the same person before it can be changed in the social security center.