Can I still use Profane Memento if I have out Silent Gravestone?
Silent Gravestone has no interaction with Profane Memento. Silent Gravestone's static ability says


  Cards in graveyards can't be the targets of spells or abilities.


Profane Memento's ability does not try to target anything in graveyards or otherwise. It simply reacts to cards moving into the graveyard. So, the ability keeps working even if you have Silent Gravestone on the battlefield.