Position function allows only string as pattern parameter:
 
select position(sub-string in string)
 
If you are looking for more than one sub-string you can't do it with a single call to position.
More info: 
https://stackoverflow.com/questions/51925037/how-to-find-position-of-multiple-sub-string-in-postgresql
 
 
Required solution: make sub-string accept regular expression just like the LIKE operator.