I want set up buttoms when clicked on will open files attached to the pdf in the attachment pane

Is the other file a PDF? If so, you can easily set it up. Select as the action of the button the "Go to a page" command, then when the floating window with the "Set Link" button appears, open the attached file and browse to the desired location in that file, and then click that button, and you're done!

Please provide a screenshot.  What do you mean by you've attached files and they do not show in the attachments tab?

Attachments are opened with the "doc.exportDataObject()" function.

Here's the reference entry:

https://opensource.adobe.com/dc-acrobat-sdk-docs/library/jsapiref/doc.html#exportdataobject

Opening attachments is a privileged operation, so it can't be done from a document button script alone.