Curve Number Calculation

ArcGIS Pro

First, you need to download the Annual NLCD (National Land Cover Database). You can download it from LINK.
You can download as well the HSG (Hydrologic Soil Group) shapefile from LINK.

BUFFER TOOL
Use it to create a smaller watershed shapefile inside the original watershed shapefile. Follow this tutorial.

You have to do it because you will use it to clip the the NLCD raster, and in order to have all the cells of the raster inside the original watershed boundary, you have to clip it with a slightly smaller one.