Hello @KimberlyR959 ,
At this time, phone numbers aren't a column that can be selected and viewed / sorted in the Contacts page. My advice, as far as tracking down every contact that's provided a phone number, would be to export your contacts as a CSV file, then use your preferred spreadsheet editing program to sort the column for phone numbers so any blank contacts are filtered down. With this, you'll at least have an idea of how many contacts have provided you a phone number.
That said, contacts that have opted into receiving emails may not have necessarily opted into receiving text messages. This is why SMS number and permission status are separate contact fields in our system, since there's an entire other world of regulation and anti-spam that we and our customers must comply with. Make sure to check out our SMS permission policy, as well as our article on importing SMS contacts.
For a quick-reference for various SMS-related articles and getting started with SMS marketing, I'd recommend checking out this response in our Community.
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