How to change Oracle default data pump directory to import dumpfile?

I want change default directory dumpfile.

You could create a new directory and give it required privileges, for example:

SQL> CREATE DIRECTORY dmpdir AS '/opt/oracle';
Directory created.

SQL> GRANT read, write ON DIRECTORY dmpdir TO scott;
Grant succeeded.

To use the newly created directory, you could just add it as a parameter:

DIRECTORY=dmpdir

Oracle introduced a default directory from 10g R2, called DATA_PUMP_DIR, that can be used. To check the location, you could look into dba_directories:

SQL> select DIRECTORY_NAME, DIRECTORY_PATH from dba_directories where DIRECTORY_NAME = 'DATA_PUMP_DIR';

DIRECTORY_NAME       DIRECTORY_PATH
-------------------- --------------------------------------------------
DATA_PUMP_DIR        C:\app\Lalit/admin/orcl/dpdump/

SQL>

With the directory parameter:

impdp system/password@$ORACLE_SID schemas=USER_SCHEMA directory=MY_DIR \
  dumpfile=mydumpfile.dmp logfile=impdpmydumpfile.log

The default directory is DATA_PUMP_DIR, which is presumably set to /u01/app/oracle/admin/mydatabase/dpdump on your system.

To use a different directory you (or your DBA) will have to create a new directory object in the database, which points to the Oracle-visible operating system directory you put the file into, and assign privileges to the user doing the import.