Where I can find video mp4 on Internet?

Answer 1

search on google. mp4 is most common video format

Answer 2

There are a bunch of sites which offer example clips in MP4 format. Give it a search as endorsed by Rellot. E.g.

https://samplelib.com/sample-mp4.html

If this weren't SL Q&A, I'd have a few more spicier examples...