“MBR2GPT.EXE converts a disk from Master Boot Record (MBR) to GUID Partition Table (GPT) partition style without modifying or deleting data on the disk. The tool is designed to be run from a Windows Preinstallation Environment (Windows PE) command prompt, but can also be run from the full Windows 10 operating system (OS).[…]”

https://technet.microsoft.com/itpro/windows/deploy/mbr-to-gpt

https://blogs.technet.microsoft.com/windowsitpro/2017/04/05/whats-new-for-it-pros-in-the-windows-10-creators-update/

https://redmondmag.com/articles/2017/04/07/windows-10-creators-update-tools-and-documentation-released.aspx