You cannot file for an extension because it is too late. The deadline to request an extension was midnight April 15, 2019. Now your return is just late.
If you are getting a refund, there is not a penalty for filing past the deadline. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.