Windows 10: Legacy To UEFI BIOS problem

I have a DELL Optilex 990 so when I go to my bios I go to Boot Sequence then I switch to UEFI and the Boot Sequence is empty. When I boot up my Device it says no bootable devices found. How do I fix this. Please tell me the file path to Windows Boot Manager because I still want to stay at UEFI boot.

:)

 

Problem Regarding Bios Change from UEFI to Legacy

I have hp pavilion p045tx with windows 10 pro. I recently install Ubuntu with windows 10 so for that I convert my bios setting from UEFI to Legacy mode for install third party software like wireless Driver and all in Ubuntu.
But after every restart the bios setting change to default and that is to UEFI mode and that will cause an problem of no OS detect. Every time I have to go to bios setting and enable the legacy mode to start my OS. Can anyone suggest me what to do in this
case.

 

Legacy to UEFI

I'm debating moving to UEFI form my now legacy BIOS (Award Software Int.) the mother board is a GA-Z68XP-UD3 rev1.0 on the the following link it shows a UEFI BIOS U1J )UEFI BIOS)

https://www.gigabyte.com/Motherboard/GA-Z68XP-UD3-rev-10#support-dl-bios

Currently I'm running the legacy F10 BIOS. Does installing the UEFI BIOS automatically take care of everything to get to the UEFI BIOS? Installing the UEFI BIOS following the instructions using the Q-flash method GIGABYTE How to Reflash Motherboard BIOS

What's steps do I take and in what order?

Much appreciated

 

[Problem] UEFI card on a legacy BIOS Mobo!

AFAIK, almost all UEFI video cards have hybrid BIOSes so they will work with either UEFI or legacy motherboards. If it was a UEFI only card, then it wouldn't even boot in a legacy BIOS motherboard.