This article explains which data types ProBackup can restore for Basecamp.
To-dos
When you restore a to-do, a duplicate is created in the related list.
Messages
When you restore a message, a duplicate is created in the related project.
Uploads
When you restore an upload, it is added back to the related project.
Attachments
When you restore an attachment, it is added to the related item.
Table cards
When you restore a table card, a duplicate is created in the related project.