To play Samurai Warlords games you will need a fresh clean install of MTW/VI/patchv2.01
The CD Key you need to install is the one for VI
All letters are Capitals and any '0' is a zero and put in the '-'s

If you still get the Invalid CD Key message check out this thread
https://forums.totalwar.org/vb/showthread.php?t=86937