To report the conversion contribution for 2016, you would complete part 2 of Form 8606. https://www.irs.gov/pub/irs-pdf/f8606.pdf. However, I think there is a problem with your 1099R because they have 10,926 in box 2a as a taxable amount, and you only had nondeductible contributions to your Traditional IRA. Did you file Form 8606 each year that you made contributions to the Traditional IRA to identify these contributions as nondeductible? Also, when the conversion contribution was made to your Roth IRA, that should be reported to you on a Form 5498 in box 3, "roth IRA conversion amount"https://www.irs.gov/pub/irs-prior/f5498--2016.pdf.
