Converting MV4 files to a format that works on WD

Just got a WD elements play multimedia drive. Managed to put all my films on it, that I bought from
iTunes. But unfortunately the file format does not play on it. It suggests converting them. I have tried lots of file
Converters but none of them have worked. Can anyone please suggest one that works for films from iTunes. Bear in mind they are long so are quite a bit of GB. Thank you

No, you can’t.  Those files are all encrypted due to DRM.   You can only play them on devices that Apple authorizes.

Note this page:

where it says:

File Formats Not Supported
Does not support protected premium content such as movies or music from the iTunes Store, Movielink, Amazon Unbox, and Vongo

Not even trying to remove the DRM of the movie will help.