How to upgrade my merciless iron daggers into dark silver ones?

https://preview.redd.it/fd6utuojyvdf1.jpg?width=1920&format=pjpg&auto=webp&s=353e931ef44a2819f7517d5654ec689e0f2fb759

I was wondering how i can upgrade my keen piercers into the dark silver ones. It clearly says upgrade cost 1/1 dark silver daggers but I couldnt figure out how to. I already tried doing it on the ancestreal forge, but it wouldnt let me. What am I doing wrong? Can i even upgrade modfied merciless iron gear into dark silver?