Hi wellcome here
Pre – requisite for database conversion
Patch set for 10.2.0.2.5 should be installed
Time version must be >= 4
Install the Oracle 11g on another ORACLE_HOME
Note: We cannot upgrade the existing Oracle Home, since 11g is not a patchset. We have to install 11g oracle home as a separate ORACLE_HOME in parallel to 10g Oracle Home.
follow the below link