Using strain gauge to measure deformation and stress

I plan to use a strain guage + HX711 and arduino to measure stress and deformation on a metal beam while applying some load , what i don't understand is how should i go about writing the code and how do i convert the raw data i would get to computer values. I want my final output to be in stress or strain

Thank you for your help in advance!

You have to know how the load deforms your beam. Then apply these formulas in reverse for mapping back the strain into load values.

Or you record (load, strain) value pairs and map the values by interpolation of that table.