how do I get 2023 schedule OR-ASC code 307 , federal pension credit

This is actually a subtraction from your income, rather than a credit against your tax.  To receive the subtraction, you first want to make sure that you identified your pension as coming from federal employment.

To get back to the relevant portion of TurboTax Online:

1. Select Tax Home in the left pane
2. On the Hi, let's keep working on your taxes! screen, select the dropdown to the right of Wages & Income
3. Select Start, Pick up where you left off or Review/Edit, as appropriate
4. Scroll down and select Edit to the right of IRA, 401(k), Pension Plan Withdrawals (1099-R)
5. On the  Here's your 1099-R info screen, select Edit to the right of the 1099-R related to your federal employment
6. Page through the screens until you get to the Where is your distribution from? screen
7. Select the bullet next to Federal government retirement benefits, then select Continue
8. Continue through the retirement screens.      Once you get to Here's your 1099-R info, select Continue and answer any other questions
9. Answer  Yes on the Did you get a 1099-R in 2023? page 

Once you're back to the Great! We've got your income info screen:

1. In the left pane, select the dropdown next to State Taxes
2.  Select Your State Returns
3. Select  Continue to the right of Oregon
4. Proceed through the Oregon screens until you get to the Here's the income that Oregon handles differently screen
5. Select  Start or Revisit to the right of IRA and Pension Distribution Adjustments
6. On the  IRA and Pension Distribution screen, select the appropriate box(es).  If you received federal pension income for federal service before October 1, 1991, make sure you check the relevant box.  Then, select Continue
7. On the  Review Federal Pension Benefits screen, select Continue
8. On the  Federal Pension Summary page, you'll see a list of your federal service pension distribution(s).  You can enter your service dates and points by selecting Edit to the right of your relevant pension
9. On the  Enter Federal Service Information screen, enter your relevant information, then select Continue
10. Back on the Federal Pension Summary page, if you have no further changes to make, select Done

If you're eligible for the income subtraction, TurboTax will make it for you.

For subtraction eligibility information, see Federal pension income [ORS 316.680(1)(e)] in Publication OR-17.