Importing HEIC files

Just visited an archive this week and took some pictures with my iPhone 8, running iOS 12.1. After transferring these photos onto my iMac I went to upload them into my Tropy file, but was unable to select any of the images. I realised that they all had HEIC file extensions (hitherto new to me) and appear to be some new Apple extension for photos. Any idea how I might be able to import into Tropy (running 1.3.1)? Should I simply change the file extensions manually to jpg? Or, is there another way to import these photos to Tropy? Thanks in advance.

Have you tried any of these online solutions?