Create table T_CST(
a Number,
b varchar2(4000));


insert into T_CST Values (1, '006CSTTYPE87643212410CID');

insert into T_CST Values (1, '00789CSTTYPE987654310CID');

insert into T_CST Values (1, '0034908CSTTYPE4062190CID');

commit;

SQL> select a, b, substr(b, instr(b,'CSTTYPE')+7,5) val from t_cst;
         A B                        VAL
---------- ------------------------ -----
         1 006CSTTYPE87643212410CID 87643
         1 00789CSTTYPE987654310CID 98765
         1 0034908CSTTYPE4062190CID 40621