hey @faramirza,
Which interfaces did you try already with no success? removable-media covers /media, /run/media and /mnt. I believe you might also need mount-observe.
Running snappy-debug can help you identify other interfaces needed.
You might wanna check the https://snapcraft.io/duf-utility and related discussions such as Alias duf on duf-utililty & auto connection and Classic confinement request for duf-utility.