help! How to make a hard copy photo album from iCloud

Ive tried to transfer my iCloud photos to my desktop of my MacBook pro, and upload that into shutter stock to make my own hard copy photo album, but they don't accept HEIC, and somehow all my photos are in that format, as opposed to JPG. Not sure how this happened, but I have a couple of years of photos using HEIC! Can someone advise what company to use to transfer my iCloud photos to the print company to make the albums apple used to allow us to make and print out? Or perhaps an easier process to make an album? My preference is not to have to download a software program that converts HEIC to JPG as that seems too complicated. Perhaps there is an easier way to do this! thanks