Here we are going to convert a NON-CDB to PDB.
The process is simple , from the 12c Oracle Home start DBCA and create a CDB Instance with one PDB. Then you have all the necessary setup for the migration. Now with few simple steps one can migrate to the CDB instance.
In this demo my Non-CDB name is DIEGO and the newly created CDB instance name is GLOBALDB, it has one PDB named PDB001 and will later add DIEGO into the CDB as a PDB.