Why can't ffmpeg see the files?

Question

fmpeg

I want to make video from frames. I have frames in the folder, through the folder I go to the command line, write dir, all files are visible. But when I want to make a video, it says that the files could not be found.

Answer 1

-start_number must be specified
https://superuser.com/a/666994

Answer 2

And why is there a letter d at the end of the command in the file name?