how many picture i need, to post video
cant find it

Im not sure what you mean.

They want to know how much they need to contribute to upload videos. You can't post videos until you reach a certain trust level.

There is no public answer, and there is no concrete "how many." The fact that your uploads still need mod approval says your trust level isn't very high. Uploads, comments, forum posts, good faith tagging will all improve your trust, which will enable you to post videos. There is no exact number. Be good and you'll get the right eventually.

I've heard that you need to post 5 images before being able to post a video. I dunno if it's still the right answer, maybe it's outdated

It should still be 5, that’s exactly how many I needed to start posting videos.
Keep in mind that having a post get deleted/not approved actually removes one from your total post count, in my case I had 2 of my 5 get deleted before even posting them, so I actually had to post 7 (not including the deleted ones) to get video perms.

At least, that’s how it worked for me. Posts were the only thing I COULD do besides tag edits and such, since I didn’t trust the forums and also didn’t comment at the time..