Hi Irwan,
VariCad file converter is free and the size is very legitimate, only 39 MB.
Download link--https://www.varicad.com/en/home/products/download/

So,you can download and install the VariCAD Viewer 2019 3.05 and convert your file.
Otherwise you can send me the .DWB file, I can try to convert it to Step 3d/DWG as a volunteer purpose only.
My email id is - spoonandbolt@gmail.com.
Thanks,
Shovon