For each audience you exported, you'll need to import each CSV for the subscribed, unsubscribed, and cleaned contacts into your main account. It's important to take the time to import each file with the right contact status so you don't inadvertently add an unsubscribed contact as subscribed, or vice versa.
To keep the drag-and-drop templates, we recommend you use the Share feature to move the templates from your old accounts to your master account. You can directly import the HTML templates from your old accounts into your master account, but you'll no longer be able to use drag-and-drop content blocks.
To preserve your audience statistics and other data, pause your monthly billing or archive contacts to keep your old accounts open but inactive. If you don't need to store data in your old accounts, you can close them.