where to enter roth to ira conversion?

You will do this in the Wages and Income section under IRA, 401(k), Pension Plan Withdrawals (1099-R).  If you didn't get a 1099-R, and you are re-characterizing ROTH IRA contributions to Traditional IRA contributions.  This is done in the Deductions and credits section under Retirement and Investments.  See the following links for more information on how to enter this in TurboTax:

• How do I enter a backdoor Roth IRA conversion?
• How do I re-characterize a Roth IRA contribution as a traditional IRA contribution in TurboTax?