I am adding and rerouting circuits from an old screw in fuse sub-panel (soon to be replaced) to the outdoor service entrance through the crawlspace. The entrance panel is mounted on the exterior wall 10" above the rim joist so I can't come through the back. Do I run the NM cable through a PVC conduit elbow into the box? How do I secure the cable to the box (code)? If I can do this, how many 12ga & 14ga cables can go through what sized conduit?