I'm referring to Pyroclasm. I want to make sure it deals damage to all creatures on the battlefield.
Barring multiplayer range of influence rules (see comprehensive rule section 801), each creature means that each (therefore, every) creature on the battlefield will be dealt damage.
If you're interested in the nitty-gritty comprehensive rules which spell this out, this is a consequence of comprehensive rule:
A particularly tricky opponent could Ghostly Flicker their Blinkmoth Nexus in response to your Pyroclasm and save it. When the 'Flicker resolves, the Nexus would return to the battlefield having no memory of being a creature a moment before.
"creature" means "creature permanent" which means "creature card or token on the battlefield".