Drop a TAdvGridReplaceDialog on the form and a TAdvStringGrid.
Add the code:
Fill in the dialog a value that can be found in a grid cell and a value it should replace and press "Replace All".

TAdvGridReplaceDialog is not applicable for TDBAdvGrid, only for TAdvStringGrid. This is because, to change values in the TDBAdvGrid, values should be changed on dataset level, via DBField, not just with grid.Cells[].