Start Diablo II LoD. Do not load your character directly. Instead, click and observe the character list. The game will display a message: "Converting character files to newer version. This may take a moment."
In Diablo 2: Lord of Destruction (LoD) , patching typically maintains backward compatibility for offline character save files, but the directory where these files are stored changes depending on the version you are running. Save File Locations by Patch diablo 2 lod character save files patched