@shunlvswx Do you mean the household inventory or the personal inventory?
In personal inventory, you should be able to click at the top right corner of an item to sell the entire stack.
In household inventory, if you click on an item, a pop-up appears that lets you increase or decrease the quantity of that item you wish to sell. (Yes, you need to click, click, click....)
My games always start lagging after a few generations so I feel for you!
I try to minimize items in both personal and household inventories.
Before you move, place any furniture/objects you wish to keep into your family inventory.
Then, at the Move menu, select Sell Furnishings to receive cash for whatever you've left behind; they won't appear in your new home's family inventory.
This won't help you for your recent move but perhaps for the next move.
Best wishes and happy simming.