When I open photos in iMovie and go up to albums not all my albums in the photos app show up.

Make sure that you have clicked on the All My Albums item to the right of the Albums selection. It looks grayed out, but no matter. That should get you all of your albums.

Also, iMovie will only reference media that is in your system photos app library. So if some of your albums are located in other Photos app libraries then those would not show up.

{Edit} Further, media that is in the cloud, such as if using iCloud Photos with optimized storage selected, would not show up. Such media would need to be downloaded first.

-- Rich