To search for an unmatched quote, surround the quote with a pair of alternate quotes (i.e. wrap a double quote in a pair of single quotes, wrap a single quote in a pair of double quotes).
If a single quoted string of text does not contain any blanks then any internal double quotes will be included as part of the searched text. It is also true that if a double quoted string of text does not contain any blanks then any internal single quotes will be included as part of the searched text.
If an internal quote is unmatched in a search string, then the internal quote is treated like a search character.
For example:
FIND(' HELLO "THERE')
will search for the strings HELLO and “THERE.
To make the FIND() function return a true value where multiple search strings are found within in individual fields (not the same field), then you must concatenate the fields together within the FIND() function as field1+field1+field2+field3).
For example:
FIND('commercial "real estate"',COMPANY+DESCRIPTION)
will search for BOTH “commercial” and “real estate” in EITHER the COMPANY or DESCRIPTION fields.