How do I upgrade a great maul to thunder maul

Horadric Cube Recipes (Weapon Upgrade)
Normal to Exceptional (Unique): Sol + Ral + Perfect Emerald
Exceptional to Elite (Unique): Lum + Pul + Perfect Emerald
Normal to Exceptional (Rare): Amn + Ort + Perfect Sapphire
Exceptional to Elite (Rare): Um + Fal + Perfect Sapphire

Only works for unique set or rare items

1 Lum Rune + 1 Pul Rune + 1 Perfect Emerald + Unique/Rare Great Maul

You can't upgrade white item.

rare only fal um Psappire