Neither a 401(k) nor a 403(b) is an IRA. Enter amounts shown in box 12 of your W-2 only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax. Employer contributions to a 401(k) or 403(b) are not reportable anywhere on your tax return.
The only circumstances that you would enter a $2,600 IRA contribution is if the money was simply a direct-deposit of part of your pay into a regular personal IRA as a convenience provided by your employer rather than the money being paid to you and you depositing the money into the IRA yourself, but it appears that the account that received this deposit is not an IRA.