Hello,
There are several issues with your question:
- there are no subbasins in swat+ :)
- the cn2 is adjusted every day of your simulation, so which value do you want, exactly?
The average cn for a period is reported in the XX_wb_timestep.txt output. For landscape units (not subbasins) see the lsunit_wb_aa.txt output, where the cn is reported in the column named "cn".
Best,
Natalja