I recommend to read the docu: Transfer of Warehouse Stocks: Process Flow - LE - Logistics Execution - SAP Library
Navigate on the left and use the Examples for the Warehouse Management System
to map your case.
Then see the program RLBEST00 and the structure RLBES which has a field for the target SU Number: NLENR
Do you really want to create new SU numbers and re-label all your inventory?