Game Disaster

I was working on a game for awhile in Unreal Engine 3.12.5. Everything was going great:) I could walk around.
I could jump and it felt like I was in outer space because I adjusted the gravity. I was running out of space on
my computer so, I deleted every version of Unreal Engine 4 besides the latest and greatest Engine. Unreal Engine 4.13:)
So, now when I run Unreal Engine 4.13 ever time I load up my game and try and run around and interact with my levels I am floating around.
I am not a character with a gun. I am just floating around my level. How do I fix this?

Have you checked what game mode the level is set to use?