Go to takeout.google.com/transfer while signed into your Workspace account. This copies Gmail and Drive files you own directly to your personal account. Takes hours to a week. The verification code expires in 24 hours.
Known limitations:
- Only covers Gmail and My Drive files you own
- Does not include contacts, calendar, tasks, or chats
- Files in "Shared with me" or Shared Drives are not included -- move them to My Drive first