Javascript Async/Await inside promise

Question

I have methods in a class as below. The await in callback doesn't work. If there is duplicate item, available_quantity inside Api.get should be updated for next item but same quantity is displayed. I think i have used Async/Await properly but still it doesnt work. Please help me solve it.

async checkItems(callback){
    for(const items of (this.all_items)) {  
        let newItem = items.product_id.id;  //item id
        let added_quantity =items.quantity; //total quantity to buy
        await Api.get('materials/get/'+newItem).then(async (data) => { //gets item data from inventory
            let available_quantity = data.quantity; //get total quantity available in inventory
            if (added_quantity <= available_quantity){ //if total quantity available in inventory is greater than buying quantity

                await callback([newItem,(available_quantity - added_quantity)]); 
               //all i want to do is wait for this callback to complete before moving to next item in for loop.

            }
            else{
                items.quantity = 0; //if total quantity available in inventory is less than buying quantity set the buying quantity to 0
            }
            
        });
            
    }
},
updateInventory(itemData){
   return Api.post('/materials/update', {
        id: itemData[0],
        quantity: itemData[1],
    }).catch(() => {});    
},

await this.checkItems(this.updateInventory);