Where can I find the attachments/files users upload into the WebHelpdesk other than looking at each ticket?
The attachments are stored in the database. There isn't (as far as i'm aware) a method to query/list out all attachments directly within the product.
One way you can get attachment data is by doing API calls to read the attachment data out...but that would require someone to write a script or something to pull that data.
Web Help Desk REST API Guide