@deeva ,Hello, log into One Drive from your device.You may have logged out.
2.Check the Trash if you have accidentally deleted them.
3.In Gallery / Albums Settings, check that they are not hidden.
"The quieter you become-the more you are able to hear..."
@deeva: If you still have your S8 then I recommend using Smart Switch to transfer your photos over to the A12.
If you have registered the same Google account to your A12 I'd also recommend connecting to Wi-Fi and swiping up from your Home Screen > Google (folder) > Photos, as you should find an archive of your images stored here.