I saw someone made an International community but couldn’t find it on my instance, so I made a Lemmy.ml one

Your home instance will only receive posts to a community on a remote instance once at least one user on your home instance is subscribed to that remote instance's community. If you're the first one, you need to trigger a search for it, then subscribe, and then your home instance will start getting posts.

I'm going to go to Lemmyverse's community list to search for it:

https://lemmyverse.net/communities

I would guess that it's !international@lemmy.world.

It currently has no posts:

https://lemmy.world/c/international

Your home instance, lemmy.ml, doesn't yet know about it. Here's the link to your home instance's view of it:

https://lemmy.ml/c/international@lemmy.world

The community international does not exist on this instance (yet). This can happen if you are the first person to try and open it in this instance. Someone will need to prompt this instance to fetch the community from the original instance. This task can be trigerred by entering the community URL (ex. lemmy.world/c/international) or identifier (ex. !international@lemmy.world) into the search page (reference).

You can do this by clicking on the button below, and then coming back after some time. Don't worry about the "No results" message, the fetch process would have started in the background. Alternatively, you can copy one of the codes above and do the search manually at https://lemmy.ml/search. You can also just view the community on the foreign instance.

If you want it to, go to the above link I made to your home instance's view of the thing, click "trigger a search", and then subscribe to it, and if/when people post there, you'll get posts.