Since you do not have a Workbench disk, the only way to get adf's on floppy is by buying a "Catweasel" disk-controller. This also supports floppies for all kinds of systems like the C=64, MSX, Atari, and many other disk formats. Otherwise, obtain a Workbench disk plus 'Amiga explorer' from Cloanto (there's also a freeware alternative on Aminet, but you have to have AmigaBasic, wich I did not have, so I did not test it.)
