How to Read Data Sentinel 1A

Hallo sirs.
I want to ask

  1. how do we read the value of Sentinel 1 data in accordance with the desired data for example in reading the value of soil moisture ?
  2. And are there criteria in determining the level of soil moisture at the study site ?
    like Backscatter value -13,6578 = medium soil moisture or -1, 3678 = low soil mositure at the study site

I hope anyone can answer my questions

Sentinel-1 does not store soil moisture as a separate information. Moisture does affect the backscatter intensity of SAR signals, but so does surface roughness and vegetation cover, materials ect…
So there is no direct relationship between S1 backscatter and soil moisture. There are global missions (SMOS) which deliver soil moisture, but at a coarser scale.

Maybe these materials help you for a start:

There are approaches to estimate soil moisture from radar data but they require field data, multiple images, or advanced workflows. They are discussed in many topics already, so I suggest to go through these topics and continue the discussions there:

Thank you, sir, for agreeing to answer my question.
it means that based on your opinion, valid data for soil moisture using Sentinel-1 data still does not exist. only we can provide a comparison between Sentinel-1 data and Field data. Isn’t that right sir?

yet, there is no direct application which automatically translates S1 backscatter to soil moisture.
But you can relate field measurements to backscatter with the correlative plot view (last topic I linked)