Em editor phone number formatting

I have phone number/number look like this xxxxxxxxxx I want to turn it to this formatting on em editor xxx-xxx-xxxx Basically 3 digit -3 digit -4 digit like an USA phone number.

How can I do it?

Formatting phone number

Use Replace. Find the Regular Expressions pattern (\d{3})(\d{3})(\d{4}) and replace with \1-\2-\3. The pattern looks for a string of 10 digits and then uses backreferences to put dashes in between the digits.