We can help you transfer all the emails from LinkedIn to your own database.
LinkedIn lets you download the emails of your 1st level connections. To do so you need to follow the steps in their 'how to' page:
https://www.linkedin.com/help/linkedin/answer/66844/exporting-connections-from-linkedin?lang=en
The result of following these steps is an email sent to you with a .CSV file as attachment. The file contains the list of emails, names, current job and company and other information.