SQL> create table t (col integer);

Table created.

SQL> insert into t values(9999999999);

1 row created.

SQL> select regexp_replace(to_char(col),'([0-9]{3})([0-9]{3})([0-9]{4})','\1-\2-\3')
  2  from t;
REGEXP_REPLACE(TO_CHAR(COL),'([0-9]{3})([0-9]{3})([0-9]{4})','\1-\2-\3')
-------------------------------------------------------------------------------------
999-999-9999

1 row selected.

    select pno,
  2   substr(pno,1,3)||
  3  '-'||substr(pno,4,3)||
  4  '-'||substr(pno,7,4)
  5* from phone_format1
SQL> /

       PNO SUBSTR(PNO,1
---------- ------------
5614317567 561-431-7567
5614317567 561-431-7567
5614317567 561-431-7567
5614317567 561-431-7567
5614317567 561-431-7567
5614317567 561-431-7567