Download OneDrive onto new MAC Sequoia

I have plenty of capacity now and want to keep my files, especially my pictures, on this MAC using OneDrive as a backup and for sharing with other devices. However, when I went through the setup and selected that option, only an old tree of photos was selected, and none of the recent/current photos appeared. Thousands of photos show on the MS Photos program on my PC, dating back to the last century! They are also visible when viewed on my iPad when selecting OneDrive, where the screen presented is the same as the Photos screen on the PC with the Photos title and my avatar. Selecting OneDrive>view online on the MAC also displays all the photos, although that iconic screen heading is different.  

There may be an issue with a second program on the PC, PhotoGallery, which was used before the Photos program existed. This is the file tree that was transferred and used until 2018. So, are the current images just floating there unfiled? There appears to be a sync issue, and I want to check to be sure they are qued to sync with OneDrive. Possibly, I could select and move them manually. What/where is the file holding the pictures in Photos so I can choose to download them manually? I found I can't simply pick them up and move them to a new location like I do on a PC.