Question: when do piccolo and kami fused?
Answer: In Dragon Ball Z: Kakarot, Piccolo uses Namekian Fusion to fuse with Nail during Frieza Force Saga Episode 6. Fusing with Nail only gives Piccolo a lot of EXP. However his later fusion with Kami appears as a transformation called True Namekian Fusion which allows Piccolo to access his Super Namekian power.