ebook-convert settings problem

Hello everyone, I already apologize for the question, but I could not find any information about it.
I tried to convert, via the command line, an ebook in .epub format to a .mobi caliber format, inserting options, but they don't seem to work.
I would like to have the first image removed from the file during the conversion and then inserted the one from the metadata.

The command I entered is this:

Is correct? Unfortunately the result doesn't return what it should. In fact the file is converted without these options.
Thanks in advance for the help.