how to open the SLDWLDTBT file?
That should be a weldment cut list table Template.
If you are trying to USE a specific table template, then you should be able to use it when you are creating a drawing (I guess you can add a cutlist to a 3d model as well).
Then just select the template file.
To CREATE a template file, just add the default cut list table, modify it how you want, then RMB the table and select Save As...
EDIT: Also see this: 2015 SOLIDWORKS Help - Weldment Cut List PropertyManager
Retrieving data ...