We’ve been asked many times what can be done to migrate all the data from MailChimp that is a true asset of our current customers. As a result, we developed a direct importer of data from MailChimp.
The only thing you need to do is to go to Settings → Import Data. We ask for your patience since the bigger your database is, the longer the import will take.
There are two fields you need to fill, username which is used to login to your MailChimp account and API key as a password.
Get your API Key at https://<your_region>.admin.mailchimp.com/account/api/ - for me region was us4.