What can't you find? The exported photos or the Watermark?
Give more details aboput your question if you are having problems.
Exported photos are saved in the 'Export location' that you specify in the Export dialog.
Watermarks are 'saved' as a Preset that only exists in the LrC Catalog, not a physical file in your computer.
Correction Edit: Saved in a Watermark folder with Presets. (Thanks JustShootMe )
However if you use a graphic symbol as a watermark, this graphic file must always remain in its same folder location. If moved, renamed, or deleted, then the WM Preset will not be able to apply the watermark to exported files.