I need help making a enchantment that strikes lightning on mobs when you hit them.

you could run a procedure with the global trigger "before entity is hurt" or "entity attacked", and check if the source entity has an item with the enchantment in their main hand, then if it does use the "strike lightning at..." procedure block and replace the x,y,z of the lightning strike with "x position of event/target entity", "y position of event/target entity" and "z position of event/target entity". Or something along those lines