How to make ubuntu disk from other machine bootable?

I have two computers, this one runs windows 10. I removed the ubuntu disk from another computer and plugged in this one. The BIOS can detect the ubuntu drive, but didn’t list it as bootable.

I want to be able to boot into ubuntu and windows. I think I have to add an entry to the windows 10 EFI partition, in that partition there’s a /EFI/bootx64.efi, and I’m wondering where’s the equivalent for that in my ubuntu disk, and I don’t know where I should put it. Should it be named /EFI/Ubuntu/bootx64.efi or what?

(I’m using DiskInternals Linux Reader to access my linux partition at the moment.)