how do I convert to AAC format?

according to its description in the main page, it can read and write to AAC format.

SoundConverter is the leading audio file converter for the GNOME Desktop. It reads anything GStreamer can read (Ogg Vorbis, AAC, MP3, FLAC, WAV, AVI, MPEG, MOV, M4A, AC3, DTS, ALAC, MPC, Shorten, APE, SID, MOD, XM, S3M, etc...), and writes to Opus, Ogg Vorbis, FLAC, WAV, AAC, and MP3 files, or use any GNOME Audio Profile.

But I don't see AAC in the output format selections.

I have the following gstreamer plugins installed. Thanks

    => apt list --installed | grep gstreamer1.0-plugins

    WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

    gstreamer1.0-plugins-bad/xenial-updates,now 1.8.3-1ubuntu0.2 amd64 [installed,automatic]
    gstreamer1.0-plugins-bad-faad/xenial-updates,now 1.8.3-1ubuntu0.2 amd64 [installed,automatic]
    gstreamer1.0-plugins-bad-videoparsers/xenial-updates,now 1.8.3-1ubuntu0.2 amd64 [installed,automatic]
    gstreamer1.0-plugins-base/xenial-updates,xenial-security,now 1.8.3-1ubuntu0.2 amd64 [installed]
    gstreamer1.0-plugins-base-apps/xenial-updates,xenial-security,now 1.8.3-1ubuntu0.2 amd64 [installed]
    gstreamer1.0-plugins-good/xenial-updates,xenial-security,now 1.8.3-1ubuntu0.4 amd64 [installed]
    gstreamer1.0-plugins-ugly/xenial-updates,now 1.8.3-1ubuntu0.1 amd64 [installed,automatic]
    gstreamer1.0-plugins-ugly-amr/xenial-updates,now 1.8.3-1ubuntu0.1 amd64 [installed,automatic]