37 cards where the card types include “elemental” and the mana value = 3 and it’s legal in Pioneer

Ball Lightning (Foundations #618)
Bloodbriar (Double Masters #154)
Bloodwater Entity (Double Masters 2022 #185)
Bolt Hound (Core Set 2021 #131)
Catalyst Elemental (Core Set 2019 #132)
Chandra's Spitfire (Core Set 2020 #132)
Cloudkin Seer (Ravnica: Clue Edition #82)
Crater Elemental (Dragons of Tarkir #132)
Fertilid (March of the Machine Commander #296)
Fiery Hellhound (Magic Origins #284)
Frost Lynx (Ikoria: Lair of Behemoths #51)
Grinning Ignus (Strixhaven: School of Mages #104)
Icewrought Sentry (Wilds of Eldraine #55)
Jungle Creeper (Rivals of Ixalan #161)
Living Twister (Zendikar Rising Commander #93)
Lutri, the Spellchaser (Ikoria: Lair of Behemoths #227)
Mindsparker (Foundations #628)
Mossborn Hydra (Foundations #107)
Murasa Sproutling (Zendikar Rising #196)
Overgrowth Elemental (Core Set 2020 #187)
Phase Dolphin (Ikoria: Lair of Behemoths #62)
Regathan Firecat (Magic 2014 #150)
Risen Reef (Core Set 2020 #217)
Risen Riptide (Zendikar Rising #73)
Shorecrasher Elemental (Dragons of Tarkir #73)
Slitherwisp (Ikoria: Lair of Behemoths #208)
Titania, Gaea Incarnate (The Brothers' War #256b)
Titania, Voice of Gaea (The Brothers' War #193)
Undergrowth Champion (Battle for Zendikar #197)
Updraft Elemental (Dragons of Tarkir #82)
Vadrok, Apex of Thunder (Ikoria: Lair of Behemoths #214)
Valakut Predator (Battle for Zendikar #160)
Warmind Infantry (Gatecrash #111)
Watercourser (Battlebond #137)
Wayfaring Temple (Commander 2019 #208)
Xorn (Adventures in the Forgotten Realms #167)
Zirda, the Dawnwaker (Ikoria: Lair of Behemoths #233)

Though this query has ended, its relics still slumber in New Argive.