Can not find a distribution code in the pull-down menu that matches what a 1099-R shows.

All permissible codes are present in TurboTax's drop-down boxes.  If you have a two-character code, one goes in the first drop-down selection and the other the second.

If you can't find them, what are the codes you have in box 7 of the Form 1099-R provided by the payer?

go to my account drop down menue and click tools.