You can contact the IRS and they will help you find this number.
Please use this link to find your local IRS office. Nearly every tax issue can now be resolved online or by phone from the convenience of your home or office. If you need help from a Taxpayer Assistance Center (TAC), call to schedule an appointment. All TACs are now providing service by appointment.
https://www.irs.gov/help/contact-your-local-irs-office