To expand a bit.
Apple doesn't pick and choose what apps appear. It's up to the developer. Two things are required. One, the developer has to include the Open In extension in their app. Two, the app must tell iOS it is compatible with the file type you are trying to open.
Girdaman has already shown you where to chedk and see if your app is avialible (if not show). Be sure to check the other ...icon options as well. Open In is not he only choice/extention-type for moving a file to another app, and often not the best.
If your favorite app does not offer a method to move or copy a file from the share sheet, all you can do is contact the develoepr and ask for them to include the feautre.