How do I convert HEIC format to jpeg?

Select the photo an go to the File ➙ Export ➙ Export 1 Photo… menu option.

You can do that by exporting the file as an "edited" file with these options:

The key here is to pick JPEG. The other settings are as you see fit.

Hi

Select the image thumbnail, or multiple thumbnails if you want to export more than one.

File menu>export