Video format to play on Samsung HMX-F90
I have video files recorded on an unknown digital camera, that I need to play through a Samsung HMX-F90 digital camcorder


... why? Can't you view the files on a computer?

Copying your older files to a camcorder to view them is a very strange idea and it will most likely not work, because camcorders aren't built to do that. A camcorder (or really, any digital camera) is not like a computer that reads a card, shows you all folders and files and allows you to watch them. Most cameras have a standard path where they store their files that can't be changed. Many cameras also create accompanying files that hold metadata and the camera uses those to create the file overview in their media browser. If those files are deleted (or don't exist in the first place), the camera might not know that the files are present at all. Also, the camera will most likely only be able to read files that use exactly the same format and codec (and maybe other things, like certain metadata tags), so even if you converted your files they probably wouldn't match the output format of the camera.


  I have converted the video files to H.264 encoding and the resolution matches those recorded by the F90 camera.


That is also a bad idea, as reencoding the files will reduce their quality and is totally unnecessary just to view the files.

tl;dr: Use the appropriate tool for the appropriate task. I.e. use a camera to record videos, and use a computer to watch them.



Edit: How to do it the hard way

If for some reason you absolutely have to do it in this convoluted way, you will have to find out how the camera records and stores videos on the memory cards. Three steps/considerations for you to make your camera recognise your videos:


Correct location. All cameras store videos in a specific directory on the memory card. For example, my Canon EOS 80D stores all photos on /DCIM/100CANON/ (it creates multiple folders with incremential numbers if necessary). Your camera might allow you to change this directory (or at least define a subdirectory) in the settings. This will also allow you to find out what the default directory is. If there is no such setting in the menu, check your camera's manual for that info.
Correct format &amp; codec. If you have put your files in the correct folder and the camera doesn't show them, they might be in a format that the camera doesn't recognise. You said you converted your videos to H.264, but have you used the correct container format and audio codec as well? (More information on that in my answer here.) I suggest you record a test video with the camera and check it's metadata and file parameters using MediaInfo, then use that info to convert your video files to exactly the same format with the same parameters the camera uses. Also, note the naming pattern of the file created by the camera and rename your files following that pattern.
Keep in mind that converting your videos will likely degrade the video quality. This won't make much of a difference on a tiny camcorder screen, but do remember to backup your original files.
Cataloging files. Some cameras create catalog files alongside the actual video files that are used for the internal media catalog of the camera. If it isn't present or doesn't contain information on the videos you copied to the memory card, the camera might not be able to display them. For example, my 80D creates a .CTG file in /DCIM/EOSMISC/ for every set of images shot with the camera. However, there are also cameras that use one sidecar file per video file that may fulfil the same function. After you've recorded a test video with the camera, search the memory card for such a file and open it in a texteditor. If you are lucky, it's a plaintext file that uses a reproducible pattern that you can use to manually create the necessary files/entries for your own videos. If not, you're pretty much out of luck. You can try to look for some technical documentation on how the internal camcorder catalog works, but I doubt you would find any or that it would be any use for your situation.