HI,
If you are a corporate customer then you don't require license key or a .slf file. Your admin/purchase department have procured licenses from symantec in return symantec provided paper license which has serial key , order number, date or purchase, date of expire, produc details and quantity of licenses.
Incase you need to upgrade, please visit
https://fileconnect.symantec.com and enter the serial key which can be M123456789 format. There you can see the product which your corporate are eligible for as well as latest version of the proucts.
Rgrds,
SAM