Login with 3rd Party Credentials and Import saved addressed and CC Info

[itsalexg]

Hello! I have a unique request from a client and need some guidance. The client has a third-party customer database where they store customer shipping addresses, credit cards, and logins. This database is used on a different e-commerce platform (not Shopify). The client wants to create a Shopify site and wants customers to be able to log in using the credentials stored in the 3rd party database and have their saved shipping addresses and saved credit card info pre-populated in the customer's Shopify account. I believe the login part might be possible using MultiPass Api, but I am unsure about the addresses and CC info. I would appreciate any guidance. Thank You!