You need Multi-Instance Sub-Process or Multi-Instance Tasks:
Check out: Idiomatic solution for the 1-n problem - #3 by StephenOTT
Another variation: Splitting batch with sequential multiple instance - #4 by StephenOTT
Another variation: Pattern Review: DMN Looping for Array Input
Good Reference if you are working with JSON data: How to return a collection to be used in a multi instance sub process from an external task service? - #8 by StephenOTT