Thank you for your reply.
But I need to create 1 TO for mutiple items/SUs that is why I used L_TO_CREATE_MULTIPLE.
Using these function modules, the system will assign the destination storage bin automatically.
My requirement is how to determine the next empty storage bin for putaway, before creating the TO, so that that derived storage bin will be used as the destination bin for all of the items in the TO to be created. please note the storage type is given.