If by "VBOX" you mean Oracle Virtual Box, then I am fairly sure that allows you to create and mount shared drives/folders... you'd need to set up one for either the drive that your Bitcoin Core datadir is on, or for the datadir itself. "electrs" needs to be able to read the Bitcoin Core folder... as you pass it in with the --daemon-dir commandline argument when you start electrs.

WSL appears to have full access to the Windows file system with all my drives available in /mnt (/mnt/c, /mnt/e, /mnt/j for C:, E: and J: etc), so it's very easy... in my case: "--daemon-dir /mnt/e/Bitcoin"