Where are the form attachments located on 365?

The simplest way it is to open your site through SharePoint Designer navigate to All files -> Lists -> YourListName -> Attachments (this folder contains all attachments, that stored in current list). They will be sorted by ID. If you want to view them through the web, just click the button form SPD to view in browser.

There is no 'view in browser' option. And when I copy/paste the URL out of the Attachment properties and into the browser, it still displays as a blank list. I want to give the list owner access to the attachments list. However I can't find a URL for that. The users don't have Sharepoint Designer. 

Can you send them directly to the edit form? Or the view form, with the links to the attachments in the form? Also you could create a secondary liszt, use a workflow to get the attachments from the form, and write them to a new document Library with the list ID as a column in the document Library so you can still tie the documents to the list.

Yes I can do those things. I still can't work out why I can't navigate to the URL of the attachments via the web.