dwg to dgn conversion is typical example of CAD design export between two industry standards from Autodesk DWG to MicroStation/Bentley DGN format. Both formats are well-supported in modern software, so it should not be difficult to find one that can help you with the export.
If you do not have access to CAD software, your only remaining options are to either find someone who does and is willing to do the export for you, or you some dedicated 2D/3D converter.
Updated: September 6, 2023