Given how Windows doesn’t support EXT4 natively, you won’t be able to format such a partition using Disk Management, Windows Explorer, or Command Prompt. What you’ll need is a third-party partitioning tool like DiskGenius to get the job done. In addition to formatting, DiskGenius also facilitates some degree of EXT4 repair and recovery. Just remember to back up your data before you start in order to format your drive without losing data.