Need more advanced technical help on factory resetting my tablet

I have tried the basic stuff I could find for my Venue 8 Pro #5830 to get into diagnostics and attempt to reset or factory reset.  All it does is tell me that everything is fine and takes me back to my password screen each time it boots up.  I do not ever see "FACTORY RESET" option.  I did have to delete some things because it initially said I had no room on my tablet to do this action.  I took off games and things that would not directly affect the operating system.  I ended up taking Windows off to give me the room I needed.  I really could use the assistance to get this thing back to factory settings or where someone else can buy it and get their own log in info on it and mine off of it.  Can someone assist please?  If it does not say "Factory Reset" in any options, how can I reset it and make it mind me?