Copying Rows IF Value

I have a macro which I have been successfully using for a while and it's served me well. But now I have far too much data on my source file (55-60k rows) and I only need data the data if Column C is "AB". I'm the first to admit that I know nothing about macros.

If anyone can tell me how to make this only copy the rows where Coulumn C is "AB".

Do While fn ""
If fn ThisWorkbook.Name Then
With Workbooks.Open(myDir & fn)
With .Sheets("3-Queues by Agent").Range("A1:R60000")
ThisWorkbook.Sheets(5).Range("a" & Rows.Count).End(xlUp)(2) _
.Resize(.Rows.Count, .Columns.Count).Value = .Value
End With
.Close False
End With
End If