Slimline SATA.
Usual for laptop DVD drives. Can be directly converted to regular SATA with an adapter (I have one of those).
Alternatively, you can find a caddy for it on AliExpress for around 6 bucks. Pay attention to the height, there's 12.7mm and 9.5mm drives.
I bought this one: https://a.aliexpress.com/_Ewv1ers