if you want to download your flickr photos and migrate them to imgur you might find it easiest to use flickr organiser to create albums of 1000 photos each and download a zip of each album
if you try and download all 10,000 photos in one go you might get
Oops! We can only process albums with fewer than 5,000 photos. Please use Camera Roll or Organizr to create smaller albums or to remove photos from this one, then try again.