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If the comma will always be followed by a single space, you can try this formula.
IF(
FIND( ', ', {text field}),
'"' & SUBSTITUTE({text field}, ', ', '", "') & '"',
{text field}
)
However, this will only work if the initial string is actually a string, and not an array (such as from a lookup or linked record). It also won’t work if there are multiple spaces or no space after the comma.