Go to the <Tools><Measure> set of commands and check your geometry. If it is in mm and that is how you want to continue then use the METRIC set of units from Chip's table (mm - N - tonnes - deg C). You also need to make sure your materials are defined in the same set of consistent units as the geometry being imported. if you are using mm then the appropriate material library to use is mat_eng_mm-N-tonne-degC-mW.esp. To access it click the <Choose Library...> button when selecting a material. If you use materials with the wrong units then normal modes / frequency response analyses will give wrong answers.