You do not control another Drake or have a Drake in your graveyard.
You have another creature card in hand that is not a Drake and that does not share a creature type with a creature you control or a creature in your graveyard.
If the additional creature has multiple differently colored mana symbols in its mana cost, an additional mana of each but one of those symbols will be required.
({U} magic symbol) plus enough mana to cast the additional creature available.
Steps
Cast the additional creature by paying its mana cost.
Volo triggers, copying the creature spell.
Resolve both creature spells.
Activate Food Chain by exiling the creature token, adding at least one mana of any color that can only be spent to cast creature spells.
Cast Shrieking Drake by paying ({U} magic symbol) .
Volo triggers, copying Shrieking Drake.
Resolve the copy of the Shrieking Drake spell.
When the token Shrieking Drake enters the battlefield, it triggers, returning a nontoken creature from the battlefield to your hand.
Activate Food Chain by exiling the Shrieking Drake token, adding ({U} magic symbol) ({U} magic symbol) that can only be spent to cast creature spells.
Resolve the original Shrieking Drake spell cast in step 5.
When the nontoken Shrieking Drake enters the battlefield, it triggers, returning itself from the battlefield to your hand.
Repeat.
Results
Infinite colored mana that can only be spent to cast creature spells.