Encrypt disk without formatting? Something similar to BitLocker?

Hi. I have a 500GB Usb disk unit formatted with ext4. I need to encrypt the entire unit. All methods that I found, need to format the unit before encrypting.

I need to protect the data, not erase that or format. There's any way to do this without copy all data to another unit, format, encrypt and paste the data again? Anithing similar to Windows Bitlocker that protects the data inside the drive, without formatting?

Best regards.