List of custom objects in present system !!!!Urgent

Hi All,

I have a requirement to prepare a list of custom objects in the present system for an upgrade.

I am not sure what are the parameters I need to keep in mind while preparing the inventory.

I am new to ECC upgrade. I am not sure what are the steps involved in this.

Please let me know how to prepare the list of custom function modules and user exits for an Upgrade process.

Thanks-