docs[.]microsoft[.]com/en-us/windows/deployment/mbr-to-gpt
I'll be blunt -- I'm at a loss on why you'd want to convert a MBR formatted hard drive to GPT, but if you did [some people have talked about it in the past in GOTD comments], this *might* have a better chance of preserving your Windows 10 activation.
The only ticklish situation I can think of is if you dual boot -- can boot to more than one OS. In that case you may not have the hidden partition with boot files that Windows setup normally installs, & this will likely add it. And to add it that means the 1st partition, which might hold an OS, has to be nudged over a bit to make room. MAKE SURE YOU HAVE A BACKUP.
Whomever wrote the doc I linked to also got one thing wrong... While it varies from one device bios to the next, generally UEFI bios can boot from MBR or GPT disks, and so can so-called Legacy bios. The UEFI bios spec does call for GPT disks, but that's not enforced. In fact, Microsoft's own Windows To Go uses an MBR disk, and is designed to boot using UEFI & Legacy bios, which it does just fine.