scroll bar inventory with slot count for equip items

the picture basic draft what i want it to look like but i am unsure of how how to make it work with the UI because i want it obj that players can see if they are behind user with it open i know UI can do it but not sure as to steps i need to do have it work at all i usually use GUI in C# but the UI system i know is better for this any ideas or tips on what to do?