If you are “LUCKY” enough and have a Decent Connection you just need “REDOWNLOAD” 31GB of the game files.
1. First, you must update Apex Legends origin version to the latest version.
2. After that, rename the game folder origin version from Apex to Apex Legends (In my case, be like that)
3. After that, Move the game folder to the installation directory (SteamLibrary/steamapps/common)
if you’re afraid losing the origin version game files, then try copy.
4. Then install via steam, steam automatically discover the existing game files. (In my case, i just need download 30mb of data)
5. That’s it, you good to go.