On Sat, 26 Sep 2020, Brian Vogel wrote:

George,Give me a short list of examples that cover the range of formats you need for this to work with and I can tweak the regex.  Trying to explain how is
not something I'm inclined to do, at least not on-group, as it's really off-topic if you get hot and heavy into regular expression syntax.--

Why not just use something like this?  Untested, but it should catch periods, dashes, and spaces.
Replacement uses a comma for pausing.

Regex: \(?(\d)(\d)(\d)\)?[ \.-](\d)(\d)(\d)[ \.-](\d)(\d)(\d)(\d)

Replacement: \1 \2 \3, \4 \5 \6, \7 \8 \9 \10

Luke