For the PS5 to be able to detect saves, the root of the USB drive has to look like this: PS4\SAVEDATA\<IDString>\<YourSaves> although I didn't manage to find the IDString of GoW Ragnarok.
For the PS5 to be able to detect saves, the root of the USB drive has to look like this: PS4\SAVEDATA\<IDString>\<YourSaves> although I didn't manage to find the IDString of GoW Ragnarok.