What previous years amount do I use for 2023 state refund question?

This would be the amount of the state refund you received in 2023, for your 2022 Missouri taxes, that's taxable on your 2023 federal return. 

It won't be taxable if you either didn't itemize deductions on Schedule A of your 2022 federal return, or you elected to deduct state and local general sales taxes on your federal return, rather than state and local income taxes.

According to Line 9 -- State Income Tax Refund in the Form MO-A, Part 1 Instructions in the Form MO-1040 Instructions:

Enter the amount of any state income tax refund included in your federal adjusted gross income on Form MO-1040, Line 1 (from Federal Form 1040 or Federal Form 1040-SR, Schedule 1, Part 1, Line 1). 

If you used TurboTax on your 2022 return, the taxable amount should populate line 1 of your federal 2023 Schedule 1, Additional Income and Adjustments to Income.  To check this in TurboTax Online:

1. Open your return in TurboTax
2. Select Tax Home in the left pane
3. Select Start, Continue or Pick up where you left off under any of the categories on the Hi, let's keep working on your taxes! screen 
4. In the left pane, select the Tax Tools dropdown
5. Select Tools
6. On the Tools Center popup, select View Tax Summary
7. In the left pane, select Preview my 1040
8. On the Federal 1040 that populates, scroll down to  Schedule 1

If TurboTax has populated an amount, you'll see it on line 1 of Schedule 1.