How do I boot from my other hard drive?

Hi, I've been looking on Google for days to see how I can boot my hard drive but to no avail. I've tried so many things and nothing has really helped so far. I want to boot Windows 10 from my new SSD but I can't boot it because the Windows Boot Manager in the BIOS is still dependent on my old SSD and only starts from the old one. If I take the old one out, the Windows Boot Manager no longer shows up even though the EFI system partition is on the new one (it did on the old one too). My new SSD has a GPT file system and so does my old one because my motherboard and BIOS are very old and only have UEFI for booting, Legacy or anything else is not displayed. So I either have to move the Windows Boot Manager to my new SSD somehow, or try it via USB stick, which I don't really want to do. In the BIOS, the boot option shown is either UEFI = Windows Boot Manager (which is only there when my old hard drive is connected) or my Samsung SSD separately for booting, but that doesn't work without the UEFI Windows Boot Manager. I used cloning software to clone my old SSD completely onto my new one, meaning it had Windows on it and EFI for booting. Now my question is, how do I make my new hard drive the boot partition?

Or how do I make my new hard drive start with the Windows boot manager if it is already being used by the other SSD, or how can I move it to my new SSD????

Please help me, I would appreciate a quick answer 🙂