Where do I find my routing numbers?

Routing number for what? Bank accounts have a routing number. Please explain what you need?

For a checking account (e.g., to transfer Apple Cash)? See the following from Transfer money in Apple Cash to your bank account or Visa debit card - Apple Support

How to find your bank account number or routing number

Your bank account number and routing numbers are easy to find on your checks. If you don't have a check, you can call your bank and ask for this information.