I have a kitchen sink with a soldered cold water line attached to shut off valve. I have taken off the handle the screw and the retaining nut taken off. My question is? The stem inside the line how do you remove so I can put new washer on. Help I don't want to call a plumber?

My question is? The stem inside the line how do you remove so I can put new washer on. Are you asking how to replace a washer in a angle stop? (see image)

You put the handle back on (no threads engaged in packing nut) and turn counter-clockwise.