Where do I enter the amount of a IRA to Roth IRA conversion

Enter the 1099-R in Federal > Wages and Income > Retirement.

There will then be questions; one of them asks about conversions.

This is done in the Wages & Income section under IRA, 401(k), Pension Plan Withdrawals (1099-R). To return to this area, follow these steps:

1. Inside TurboTax, search for ira contributions and select the Jump to link..
2. Select Traditional IRA on the Traditional IRA and Roth IRA screen and Continue.

For more details, see: How do I enter a backdoor Roth IRA conversion?