How to do it properly, and then you don't have to redownload 31gb the game files.
How to Move The Game Version from Origin Version to Steam Version
- First, you must update Apex Legends origin version to the latest version.
- After that, rename the game folder Origin version from Apex to Apex Legends (In my case, be like that).
- After that, Move the game folder to the installation directory (SteamLibrary/steamapps/common)
- Then install via steam, steam automatically discover the existing game files.
- That's it, you good to go.