{2}, {T}: Exile target artifact card from a graveyard. Put a charge counter on Conversion Chamber.
{2}, {T}, Remove a charge counter from Conversion Chamber: Create a 3/3 colorless Phyrexian Golem artifact creature token.
If the targeted artifact card is no longer in the graveyard when the first ability tries to resolve, it won’t resolve and none of its effects will happen. You won’t put a charge counter on Conversion Chamber.