Final answer:
The routing identifier (RI) code is located in Block 6 of the DD Form 1348-1A in the ILS-S module.
Step-by-step explanation:
The routing identifier (RI) code on the DD Form 1348-1A can be found in Block 6. Block 6 is specifically designed for the RI code, which is a unique identifying code used in military logistics systems. It helps in routing the receipt to the appropriate destination. For example, if the receipt is for a particular military base or unit, the RI code will help direct it there.