How to correctly extract IO store container files to uasset/uexp?

Hello, I extracted some utoc IO store container files using UnrealPak, files’ UE version is 5.1, however instead of .uasset, it extracted as .uheader file. It still can’t be read by UaasetGui, a tool I was using to open and edit uasset file (GitHub - atenfyr/UAssetGUI: A tool designed for low-level examination and modification of Unreal Engine game assets by hand.). Renaming the file to uasset doesn’t work either.

I also tried ZenTools (GitHub - Archengius/ZenTools: Tools for extracting cooked packages from the IoStore container files), but it won’t extract anything.
I’ve spent days on this can’t figure it out. Could someone kindly point me in the right direction? Thanks.