Subform Auto-populate based on Main Form Drop Down

Subform Auto-populate based on Main Form Drop Down

Zoho CRM.

I have a drop down named ''number of items'' which ranges from 1-100. Below that I have a subform with 18 fields. 

Here is an example of what I need for this section: 

Number of items: 10 
Subform (all 18 fields) show up 10 times

Number of items: 30
Subform (all 18 fields) show up 30 times 

and so on... 


I have attached an image of workflow for easier understanding. How do I create this? Is there a code I need to use? 
I was wondering if there is a way of doing this through workflow?