I currently use a premixed human insulin 50:50, and I'm looking for guidance on switching to insulin cartridge. Any suggestion?

This is important to get right - different premixed insulins vary in their NPH-to-soluble ratio, and moving from one ratio to another isn't a simple swap since it can change how your blood sugar behaves through the day. I'd strongly encourage against making this switch without your doctor reviewing it first, since your dose will likely need to be recalculated. They can also confirm whether this particular strength and mix matches what you actually need.