Might be a bad download with corrupted archive, did you try to download it again?
Also from the attached screenshot it seems to be an .adf file, aren't those Amiga files? If so, there won't be any .exe files and you need to use an Amiga emulator for it instead of DosBox.
P.S. Have a look here -
Link
Third from above, I think it
is Amiga Disk File you got.