How to track the ISO invoice number

Hi,

We have 3 warehouse location in other state, So we created all the warehouses as oraganization. From here we are doing IRISO(stock transfer invoice) process and they receive the quantity and stored in their subinventory. Then they raised the customer invoice in their location. In flow wise there is no problem, but we unable to track the parent invoice number which was stock transfer invoice number.

For Example:-

For stock transfer invoice, We are using IRISO process. For example transaction between 2 units are Unit X and Y. unit X is manufacturing ,unit Y is warehouse. Unit Y raising the Internal requisition and unit X  will be process the IR through order import and ship the material to Unit Y. Then unit Y receive the material and then they will create the sales order for customer invoice and send the material to customer. Our requirement is we unable to track the received material belongs to which stock transfer invoice after complete the customer invoice in Unit Y and