If your former employee used Adobe ID type then you will not be able to access that storage without their assistance as the account is owned by them.
For Enterprise or Federated ID types (used with the Enterprise Dashboard) then your organisation owns the account and can access the data.
Manage storage in Adobe Creative Cloud for enterprise deployments
Managed access to files (Enterprise ID and Federated ID)
Creative Cloud storage is normally not accessible to enterprise administrators. However, sometimes it is necessary to access the files. For example, a user has left the organization, and it is necessary to access files in their account for use by another employee.
There is no direct administrator access to the Creative Cloud storage. For Enterprise IDs, you can force a password reset as an administrator, and then change the password to manually access the files from the Creative Cloud website.
Note:
An email with password reset instructions is sent to the user. As a security precaution, you require access to the user's email to specify a new password and access the account.
For Federated IDs, you can request a password reset and have the password sent to you via email. You can then manually access the files from the Creative Cloud website.