oracle to PostgreSQL database conversion In oracle:

select owner, constraint_name, table_name, column_name, position 
from dba_cons_columns;


Is there any table like dba_cons_columns in PostgreSQL database that we get the same information?
PostgreSQL has the SQL_standard information_schema which is actually a bunch of views backed by the pg_catalog schema.

information_schema has a fixed structure as mandated by the standard, pg_catalog is liable to change between major PostgreSQL versions.

For the information you want it's probably the table information_schema.constraint_table_usage.