MP4 format for Kindle Fire HDX

[TheTinker]

Can anyone tell me which setting to use to convert a Bly-ray DVD to a Kindle Fire HDX screen in the landscape mode? I used Generic>MP4-H264 and got a very narrowed down video.
There is no setting for the Kindle in the tabs. Don't know whether to use one of the Smartphones or Tablets settings next. The Kindle Fire HDX is 323ppi/1920x1200. It needs MP-4 files. I am thinking that the Tablets>Google Nexus 7 or 10 might be the correct setting. Anyone??
Thanks in advance

[JJ]

As most movies are 16:9 or wider, you can convert to FullHD. (1920x1080)
That will leave black borders on top and bottom, but that can't be helped.
Converting to 4:3 formats might produce a little less black borders, but you will lose part of the picture from sides.