Oracle Migration Upgrade 11g to 12c New Server
You can use expdp and impdp utility by Oracle for migration of database from 11g to 12c.

First of all we will use expdp utility to export the whole database into a dumpfile (.dmp) by issuing the following command:

expdp system/password@db11g full=Y directory=TEST_DIR dumpfile=DB11G.dmp logfile=expdpDB11G.log


Here, FULL parameter indicates that the whole database will be exported
      Directory --> The directory on server in which you want to place the dumpfile
      DUMPFILE --> The name of dumpfile
      LOGFILE --> The name of logfile (that logs the status of export process)

After the export is done successfully you will get something like:
Job "SYSTEM"."SYS_EXPORT_FULL_01" successfully completed at 10:35

Now, your whole database is stored in a dumfile(.dmp) in the 'DIRECTORY' mentioned in the expdp command.

We will now start import of the database into 12c database with the help of impdp utility.

impdp system/password@db10g full=Y directory=TEST_DIR dumpfile=DB11G.dmp logfile=impdpDB12c.log


*Before starting import you might need to transfer the dumpfile to the new server (i.e. 12c)

After import has been successfully completed you will get successfull completion message.

Reference link --> https://oracle-base.com/articles/10g/oracle-data-pump-10g

Happy Migration !!