Cantrips increase with your character level, which is independent of how many levels you have in spellcaster classes. If you are a multiclassed level 2 wizard, level 2 druid and level 2 cleric, you are a level 6 character for the purposes of Cantrip damage. The source of the Cantrip (spellcasting class, race, feat, etc) has no impact on this.
If a character has levels in more than one class, do the character’s cantrips scale with character level or with the level in a spellcasting class? Cantrips scale with character level. For example, a barbarian 2 / cleric 3 casts sacred flame as a 5th-level character. (Sage Advice Compendium V_2.0; page 11)