How Do I Convert Live Photos To GIF Files and Use Them In iMovie?

I am creating an iMovie project with around 500 photos, many of which were taken as live photos on an iPhone. I want to convert these to GIF files and stitch them together with a Ken Burns effect to create more of a movie than I would with still only photos. Can you suggest the most efficient process, please? Thank you for your inspiration, and keep up the good work.
Can this be carried out without third party software? Can the conversions be carried out as a batch or will each photo have to be converted one at a time? Will GIF files be sufficiently high quality for a movie on a large screen?
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Darren