Your FBX 3D model has wrong scale in converters mainly because the original 3D software’s unit settings (e.g., meters vs. centimeters) don’t match how the converter interprets the FBX file’s unit data.
FBX files store scale information—if the converter ignores or misreads this (like treating a centimeter-based model as meters), the scale becomes too large or small.
To fix it, ensure both your source software (e.g., Blender, Maya) and the converter use the same units. If the converter can’t adjust units, re-export the FBX from the original tool with “bake scale” enabled to lock the correct size.