First, get a stack of an item you plan on getting rid of for an item you want. Put them beside eachother in your inventory. Then when you open game, find the stack (save it in your saved list) , copy address of the pointed to value. Search hex dword of the address. Goto the 1 result, and above (forgot how many lines) is the item id.
Save that.
Go back to your stack qty.
Scroll up and you'll find the next item. Repeat like above. And copy the three pointer for that item over the 20 stack.
I would recommend doing this with the stack at 2,and freeze.