The POS function searches for a substring within a string and returns  the
  substring's starting character position.

  Example

  Y% = POS(Alpha$, "JKLMN", 1%)

1  –  Syntax

      int-var = POS(str-exp1, str-exp2, int-exp)

  Int-exp specifies the character position in the main  string  (str-exp1)
  at which the search for the first occurrence of str-exp2 starts.