Kate, click on your hard drive, scroll down to Preview, click on it and you should see your downloads. From there you should be able to see your designs you downloaded. The format does not make any difference on the computer. Being unable to download from a web site is a problem on the site, not your Mac. Good luck. Nan W
Hmmm, sorry I don't have a Mac...but I know on my Windows 10, there is a setting to ask where you want your download to go....If you don't set it, the download will default to the "Download" folder in File Explorer...looked like the download just vanished until I figured it out...took me a bit to understand that...then when I did, found all sorts of stuff there...perhaps Mac has a similar feature...and BIG Welcome to Cute!
I hope someone comes along for you Kacee. Give it plenty of time because we live in different time zones. I've already welcomed you and I'm glad that you are going to get to know our community.