>>408344636
https://answers.microsoft.com/en-us/windows/forum/all/mbr2gpt-fails-with-error-cannot-find-room-for-the/feb3c6d9-43a8-4f3a-a7a4-50e1a473f669
seems you'll need to resize the boot partition probably (very briefly skimmed literally for a second, please read the whole thing before going ahead)
I pray for you as partitioning on Windows sucks ass