Yes. In general, the plan cost is the total of your contributions to the retirement plan and that is reported in total employee contributions box.
According to page 5 of Pub 721, under the heading, "your cost", "your monthly annuity payment contains an amount on which you have previously paid income tax. This amount represents part of your contributions to the retirement plan. Even though you didnt receive the money that was contributed to the plan, it was included in your gross income for federal income tax purposes in the years it was taken out of your pay. The cost of your annuity is the total of your contributions to the retirement plan, as shown on your annuity statement from OPM........"
Please refer to page 5 of Pub 721 under the headings, "your cost" and "recovering your cost tax free" for additional clarification regarding your plan cost and how to recover that cost.
Please refer to the following FAQ for information on how to enter this form in Turbo Tax. https://ttlc.intuit.com/replies/3301403