-- EXAMPLE
select 
    '0004V0' as TESTER
    , INSTR('0004V0','V') -- OUTPUT: 5
    , INSTR('0004V0','0') -- OUTPUT: 1
    , INSTR('0004V0','0',4) -- OUTPUT: 6
from DUAL;

-- SYNTAX
INSTR(/*Main string*/, /*substring*/, /*start index*/)