You cannot search for a style that you haven't applied to the text. However you can search for the background shading e.g.
Sub ReplaceShading()
'Graham Mayor - https://www.gmayor.com - Last updated - 05 Jan 2022
Dim oRng As Range
Set oRng = ActiveDocument.Range
With oRng.Find
.ClearFormatting
.Replacement.ClearFormatting
.Font.Shading.BackgroundPatternColor = RGB(232, 198, 201)
.Text = ""
.Replacement.Text = ""
.Forward = True
.Wrap = wdFindContinue
.Format = True
.MatchCase = False
.MatchWholeWord = False
.MatchWildcards = False
.MatchSoundsLike = False
.MatchAllWordForms = False
Do While .Execute
oRng.Font.StrikeThrough = True
oRng.Font.Shading.BackgroundPatternColor = wdColorAutomatic
oRng.Collapse 0
Loop
End With
Set oRng = Nothing
End Sub