This is explained here. Basically, in your file browser in your iPhone document folder:
- Press CTRL+L to get the real address which will look like
afc://YOURSERIAL:3/
- Remove trailing colon and number and press ENTER (i.e. it should just read
afc://YOURSERIAL
)
Then, in the DCIM folder, all your pictures should be there including your .HEIC files.