Most ADL games do not have file systems on their floppy disks. As a result, disk images need to be used to play these games in ScummVM. The detection mechanism of the ADL engine uses sector data to recognize these disk images. This means that as long as the base name is the same, any supported floppy image format can be used. For example, if Datafiles lists MYSTERY.DSK as the disk image name for the game you want to play, you can use either MYSTERY.DSK, MYSTERY.NIB, MYSTERY.WOZ etc. You can find more information on the supported formats below.
Apple II disk image formats supported by ScummVM
.DSK
This is a raw disk image format with 16 sectors per track. The file size is always 143360 bytes.
.D13
This is a raw disk image format with 13 sectors per track. The file size is always 116480 bytes. This format is not commonly supported by disk conversion tools.
.NIB
This format contains so-called nibbles and is able to capture some of the tricks performed by copy protections. It supports both 13- and 16-sector disks. The file size is always 232960 bytes.
.WOZ
More information on this new disk image format can be found at [1]. This format should be able to fully capture any copy-protected disk, allowing emulators to run copy-protected software.
Transferring data from Apple II floppies
Using an Apple II computer
Later ADL games and budget releases without copy-protection can probably be transferred with ADTPro and a serial cable. If the game uses the older 13-sector formatting and/or has a copy-protection that prevents ADTPro from seeing all the data, it may be necessary to first use a tool called Saltine's Super Transcopy and then transfer the resulting disks with ADTPro. Note that even if a copy-protected disk is successfully transferred using this method, it probably won't work in an Apple II emulator, but it should work in ScummVM.
Using Applesauce and a Disk II
Using this method, .WOZ disk images can be created. See [2] for more information.
Using KryoFlux and a PC 5.25" disk drive
A major hurdle with this method is that a modern PC disk drive requires a flippy mod to read the other side of a dual-sided disk. There are some workarounds for doing this with an unmodified disk drive, but they all involve damaging the sleeve of the original floppy. After obtaining stream files of the disk, a8rawconv can be used to create a .NIB image. There do not appear to be any tools to create a .WOZ image from stream files at this time.