https://www.windowscentral.com/how-convert-mbr-disk-gpt-move-bios-uefi-windows-10
On Windows 10, you can use the MBR2GPT command line tool to convert a drive using a Master Boot Record (MBR) to a GUID Partition Table (GPT) partition style, which allows you to properly switch from Basic Input/Output System (BIOS) to Unified Extensible Firmware Interface (UEFI) without modifying the current installation or deleting the data stored on the drive.
BIOS is an essential piece of code that resides on a special chip on the motherboard that enables the connection between hardware and software. This code has been around for a long time, and while it worked pretty well, it was never designed for modern hardware, and it had many limitations, including limitations to partitions smaller than 2TB.
UEFI is the new firmware that replaces the old BIOS, and it introduces several additional features, including support for partitions larger than 2TB, and faster startup, sleep, resume, shutdowns times. Also, it unlocks many of the new security features available on Windows 10. For instance, "Secure Boot" can protect a device's startup process from malicious programs. "Device Guard" gives you more advanced controls for app access, and "Credential Guard" can help prevent pass-the-hash attacks.
In this Windows 10 guide, we walk you through the steps and information you need to know to use the Microsoft MBR2GPT command line tool to convert a drive from MBR to GPT partition style, to switch from BIOS to UEFI mode on your device.
Unlike previous methods that required to you to back up your data and perform a reinstallation of Windows, the MBR2GPT command line streamlines the process to change partition styles in minutes. The conversion is done by adding the GPT components to the MBR partition without modifying the existing partition and keeping the data untouched.
Usually, you want to start in UEFI mode from the moment you first install Windows 10. However, if you're upgrading a device running Windows 8.1 or Windows 7, or you already deployed Windows 10 using BIOS on computers that support UEFI, you can convert the drive to properly change the system firmware settings from BIOS to UEFI.
Before modifying your system configuration, we recommend checking your current settings to see if the system is set to MBR or GPT using these steps:
Open Start.
Search for Disk Management and click the top result to open the experience.
Right-click the drive (where Windows 10 is installed) and select the Properties option.
Click on the Volumes tab.
Under the "Partition style" field, if the field reads GUID Partition Table (GPT), the drive doesn't need conversion, but if you see the Master Boot Record (MBR) label, you can use the conversion tool to switch.
Click the Cancel button.
Once you complete these steps, you'll know if it's necessary to change the partition style on your device.
Also, if you need to change the partition, make sure to check your device manufacturer's support website to find out if the hardware includes support for UEFI before using these instructions.