When you say items, I am assuming you are just after a bunch of IDs… and rest of the data like name, quantity etc can be retrieved on server side, if needed.
So, you simply need a multi-select select component on the client side. Or you can use tagify component.
Then on server side, you should get an array of selected items.
There has been a recent option to have nested array data in form: Using App Connect Form Repeater with Update Record Forms
So this might be what you are looking for as well.