If we have a .dmp file that has been produced using the expdp utility, it is possible to retrieve the DDL for all objects in the .dmp file by using the following options:
impdp ... SQLFILE=myddl.sql
If the dump file has been produced using imp utility instead, the following command will give you the list of tables:
imp ... show=Y
This should tell
you the list of objects you have in your dump file before importing it.