I used linear to dB as I found in the tutorial "introduction to SNAP but then I have to use convert band. As result, what is the benefit of using convert band?
as long as you don’t apply “convert band”, your db image is just a virtual raster (indicated by the v in the symbol). This means that you can open and view them based on their logical or mathematical expression but they are not saved on your hard drive.
To convert the bands into a permanent raster, right click on the corresponding band, select ‘convert band’ and save your product with
File > Save product.
I found only when you export the virtual bands into the Geotiff or other formats, then you can save them in the right folders and used for further analysis in ArcGIS or the other GIS softwares.