traveling with frozen breastmilk..

Carlota
We're going home for vacation from UK to PH.. It's 18 hours plane ride. I have so many extra stash of frozen breastmilk that I would love to take with me since my family will help out. I don't want to not use these, there's so many. How do I store it so they won't melt? Do I check it in or just carry? How does that work with security? FTM here. Thanks!