The default template is Normal.dotm which is stored in the user templates folder If you have not changed the default location enter or copy
%appdata%\Microsoft\Templates
to the address window of Windows File Explorer and you will be taken to this folder. Note that this folder is normally hidden.
You can modify that template if you wish, but a better plan would be to create document templates for your work documents, each setup as you require for the job in hand.
Frankly the most recent versions of Word are poor when it comes to template handling, but to work around that you may find
Select Document Template useful in managing your templates from wherever they are stored.