not read paper pid key on laptop

If your COA has faded you'll need to use a Dell branded Windows 7 Reinstallation DVD which will apply Dell OEM System Locked Preinstallation which is an offline based BIOS activation mechanism and doesn't require any input of a product key. To take advantage of the Free Windows 10 Upgrade Install you'll need to perform an initial Upgrade Install and not a direct Clean Install. See here for details:

http://dellwindowsreinstallationguide.com/windows-7-sp1-iso-download/ 

http://dellwindowsreinstallationguide.com/upgrading-to-windows-10/