If you are on using the GOG version (the most common setup today), do not overthink it:
Modern GOG/Windows 10+ installs (if using compatibility/portable mode): diablo 1 save file location
Simply copy the .sv or .drv files to a USB drive or a cloud storage folder (like Dropbox or Google Drive). To restore them, paste them back into the folder you took them from. If you are on using the GOG version
The gold standard for modern Diablo 1 play. It saves files in standard user directories, not the game folder. It saves files in standard user directories, not
Older versions sometimes stored multiplayer data ( dpreview.adr or .sv files) in your Windows directory: C:\Windows .
If you're moving your saves to a new PC, just copy the entire *.sv file set to the new installation folder. Unlike newer games, Diablo 1 does not have cloud saves unless you are using a third-party launcher like GOG Galaxy with that feature enabled.