Hi Mario,
To change the millimeters to inches, please perform the following steps:
1. Open File of word or Excel
2. Click Options on the left of page
3. Click Advanced and modify like below:
If you have further questions in using Word or other Office clients, because our team focuses on Office 365 Business online services, I suggest you post new threads to Microsoft Office 2013 Community for more dedicated support. To post a new thread there, please sign in with a Microsoft account and click Participate> Ask a Question. Your understanding is appreciated.
Thanks,
Kerwin Yang