The code you posted unhides all the rows in .UsedRange. That didn't sound like what you described so, I modified it so that only those rows with a 1 in column J are unhidden. Otherwise the row's visiblity is unchanged.
This also sets the screenupdating to False while the routine runs. That makes the code run faster and avoids screen flicker.
A counter was added, as soon as five rows are unhidden, the routine stops.
Sub UnProcessData()
Dim oRow As Range
Dim counter As Integer
Application.ScreenUpdating = False
With ActiveSheet
For Each oRow In .UsedRange.Rows
If .Cells(oRow.Row, "J").Value = 1 Then
oRow.EntireRow.Hidden = False
counter = counter + 1
If counter = 5 Then Exit For
End If
Next oRow
End With
Application.ScreenUpdating = True
End Sub