That plate with the cog works with the buttonholer, the second item is part of the chain stitch attachment - it goes where the bobbin case would go.
If you look for a monogrammer - you need the one with the smaller opening.
the other one fits an open arm machine. Yours will come with the monogrammer in one box with other stuff, and the cams for it seperatly.
this is mine - one of my favorites
I have an extra box with the bottonholer and chainstitch attachment. I already found a home for the extra set of cams I had. I still have the extra monogrammer that does not fit my machine if anyone wants it.