I have a table in my database with 100 columns.
I am only interested to create a dump using expdp with only 3 specific columns from it.
Is it possible to do this directly from the expdp command?
Oracle 12c has a datapump feature views_as_table
that may work. Create a view against your source table, with just the columns you want to export, then export the view:
create or replace view view_1 as
select <desired columns> from table_1;
expdp user/password views_as_tables=view_1 directory=data_pump_dir dumpfile=data.dmp