In the below Workflow, identifying re update the filed is not working well

for each  row in SubForm

info "Add Stock in Inventory" + row.Part_Name;

rec = Add_Item[ID == row.Part_Name];

rec.Stocks_in_Inventory=rec.Stocks_in_Inventory + row.Number_of_Items;

}

 

I want to use Auto numewber to fill the Form Field but it is getting generated only on submission.

I want to add Text + Auto number for some filed. What is the option