When opening an IGES, Parasolid, ACIS SAT, CGM, STL, or STEP AP203/AP214 or DXF file, you should ensure that the DGN file into which you place the file has appropriate working units for the type of data in the imported file.

See keeping coordinate units correct for more information about setting working units when importing an IGES, Parasolid, ACIS SAT, CGM, or STEP AP203/AP214 file.