1. Sign in to dropbox.com with your Dropbox Business account credentials.
  2. Click your avatar (profile picture or initials) at the top-right corner of the page.
  3. Click Settings.
  4. Scroll down to either Connect your personal Dropbox or Link your personal account. (It might say either, depending on your account).
  5. Click Connect or Link accounts. (It might say either, depending on your account).
  6. To disconnect, click either Disconnect or Unlink.
  7. Click Sign in to connect an existing account or enter your email and password to create a new personal account. 
  8. Drag-and-drop files from personal to business as needed

https://help.dropbox.com/accounts-billing/multiple-accounts/connect-personal-account