If you are processing almost every paragraph I don't see the usefulness of using the Find command. I note that your sample has two input lists but only one of them was an autolist. This code is set up to recognise a hard-coded list by the presence of ".tab" so it works with your sample but may not work with other lists if they don't use that pattern
Code:
Sub SetupQuiz()
Dim iParaNum As Long, aRng As Range, aPara As Paragraph
Set aRng = ActiveDocument.Range 'or Selection.Range
For iParaNum = aRng.Paragraphs.Count To 1 Step -1
Set aPara = aRng.Paragraphs(iParaNum)
aPara.Range.Select
Select Case aPara.Style
Case "ans", "Q"
'do nothing
Case Else
If aPara.Range.ListFormat.ListType = wdListNoNumbering Then
aPara.Style = "t"
If aPara.Range.Text Like "*." & vbTab & "*" Then aPara.Style = "tt"
Else
aPara.Range.ListFormat.ConvertNumbersToText
aPara.Style = "tt"
End If
End Select
Next iParaNum
End Sub
Note that the code has to work backwards to avoid autonumbered list items renumbering if the preceding paragraph is converted before you process the next paragraph.