MBR/UEFI issues

My motherboard is UEFI compliant, however it was set up in MBR mode, I'm now receiving messages from Microsoft saying my PC will not be updated after 10 April because it is not set up in UEFI mode. I understand that to set up in UEFI mode all data on HD will be lost.

I understand this but I've made a back up of everything on 'C' drive including the Win 10 operating system made when operating in MBR mode. If I convert to UEFI will this back up work OK with UEFI?

This backup also includes MS Office 16 Professional , this was downloaded by an IT firm on behalf of an organisation I do some work for and I have no backup or installation disks for this although I do have the Window 25 digit key thanks to a Belarc scan. We have now parted company with this IT firm and I can't approach them. If the backup won't work then I have no way of restoring MS Office 16 that I know of.

Thank you for reading this, I'd be grateful for any help or advice

M/B is Asus A68HM-K
In BIOS are following settings.

1] Boot Device Control: UEFI & Legacy OpRom: Legacy OpRom only: UEFI only . Set at UEFI only
2] Boot from Network Devices: Legacy OpRom first: UEFI Drive first: Ignore. Set at Legacy Oprom first
3] Boot from Storage Device: Legacy Oprom first: Both UEFI first: UEFI Driver first: Ignore. Set Legacy OpRom first
4] Boot from PCi/PCI: Legacy OpROM first: UEFI Driver first: Set at Legacy Oprom first

Changing [1] from UEFI to Legacy OpRom only or UEFI & Legacy OpRom results in PC not booting and displaying following:
Recovery
Your PC/Device needs to be repaired
File\Windows\system32\winloadexe

Can only get PC to boot with [1] set UEFI

Can't really get my head round this, the m/b is definitely UEFI compliant

Not really sure what benefits of UEFI are other than ability to have more than 4 partitions.

Is next step - Convert Windows 10 from Legacy BIOS to UEFI without Data Loss Windows 10 Tutorials

Were dd you get the message I have reports locally of this as scam

Berton said:

That's what I'm trying to determine, haven't seen any other references to it. But then right now I don't have one of my MBR-only computers running, maybe tomorrow.

I have had my 2nd PC running since early this morning my time. About 9-10 hours at least and have ran windows updates quite a few times since I first saw this thread trying to replicate it. In Macrium Reflect my 2nd PC shows MBR on the disk. Also Macrium says UEFI at the top on this PC but not on the 2nd one. I will post back if I see any message of the sort. I plan on leaving the PC running for a couple days to see.