There is no particular code for a rollover of a traditional IRA to another traditional IRA.
If a distribution is paid to you and you use the money to complete a rollover to another traditional IRA, the code will be code 1 if you are under age 59½ at the time of the distribution or code 7 if you are age 59½ or over at the time of the distribution. The rollover is indicated by how you report it on your tax return, done automatically by TurboTax when you enter the code 1 or code 7 Form 1099-R, then indicate that you moved the money to another retirement account and the amount rolled over.
If you moved the money from one traditional IRA to another by trustee-to-trustee transfer where the money was never paid to you in between, it's not reportable and you won't receive any Form 1099-R for this.