Conflagrate

You cause an explosion at a point in range. Each creature in a 10-foot radius must succeed on a Dexterity saving throw or be set ablaze for the spell’s duration or until a creature uses its action to douse the fire off itself or another creature. A creature on fire immediately takes 3d6 upon failing the saving throw, or half upon success. At the end of a creature's turn, if it hasn't extinguished the flames, it takes an additional 3d6 fire damage

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d6 for each slot level above 1st.