Sql Regex pattern Find

Hi Team i need to find the position of the particular pattern in the provided string.

I have used Patindex in MSQl like below, but im not sure how to get the same output in Oracle.

Please help me on this.

the query that is used in MSQL

select patindex('%S[0-9][0-9]%','hi this is aaaaaaaa S123456789 therefor here');

O/p
21

maybe this can help you

https://docs.oracle.com/cd/B12037_01/appdev.101/b10795/adfns_re.htm