Why are all my photos pixelated and in thumbnails folder when moving to Mac?

[AC Question]

So I'm trying to move all my photos from my Sony Xperia Z5 Compact to my MacBook Air. Beforehand, I transferred everything to my Micro SD card but my SD adapter didn't work so I figured I would just plug it in and transfer everything using Android File Transfer instead. But now, after opening up the app, all my photos are in the thumbnails folder under DCIM instead of the camera folder, so when I move them on to the Mac they are ridiculously pixelated when enlarged. How can I stop them being so pixelated and back to normal quality? (These are all 23mp photos taken on my phone!) Thanks for your help.