FIND

From AgileApps Support Wiki

The FIND function returns the starting character number of a search string within a specified target string. Optionally, a character number can be specified, which defines the character from which to start. If the character number is not specified, then the search starts from the first character of the string.

Syntax
FIND('string', 'searchString', start)

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Note:
The searchString is case-sensitive. For a case-insensitive search,
use the LOWER function on both the search string and the string being searched.

Return
Number
Example
FIND('street', '123 Maple Street') = 11