Try this:

let products = [
    ["product1", "Small Widget", "159753", 33, 22],
    ["product2", "Medium Widget", "258456", 55, 44],
    ["product3", "Large Widget", "753951", 77, 88],
    ["product4", "Not a Widget", "852654", 11, 2],
    ["product5", "Could be a Widget", "654456", 99, 6],
    ["product6", "Ultimate Widget", "321456", 111, 66],
    ["product7", "Jumbo Small Medium Widget", "987456", 88, 11]
];


let sum = 0
products.forEach(product=>{
  sum += product[product.length -1]
})

console.log(sum)


let product_of_elements = 1
products.forEach(product=>{
  product_of_elements *= product[product.length -1]
})

console.log(product_of_elements)

In the end, sum variable will contain the sum of all the last elements, and product_of_elements variable will contain their products.

Yes, you need to loop. This will help you see how to access different parts of the arrays.

let products = [
    ["product1", "Small Widget", "159753", 33, 22],
    ["product2", "Medium Widget", "258456", 55, 44],
    ["product3", "Large Widget", "753951", 77, 88],
    ["product4", "Not a Widget", "852654", 11, 2],
    ["product5", "Could be a Widget", "654456", 99, 6],
    ["product6", "Ultimate Widget", "321456", 111, 66],
    ["product7", "Jumbo Small Medium Widget", "987456", 88, 11]
];

// how many items in products? (how many times to loop.)
console.log(products.length);

// get the first item (array).
console.log(products[0]);

// get the 4th item ([3]) in the 1st array ([0]).
console.log(products[0][3]);

One simple solution

const products = [
    ["product1", "Small Widget", "159753", 33, 22],
    ["product2", "Medium Widget", "258456", 55, 44],
    ["product3", "Large Widget", "753951", 77, 88],
    ["product4", "Not a Widget", "852654", 11, 2],
    ["product5", "Could be a Widget", "654456", 99, 6],
    ["product6", "Ultimate Widget", "321456", 111, 66],
    ["product7", "Jumbo Small Medium Widget", "987456", 88, 11]
];

let sum = 0;
const productItems = [];

products.forEach((product) => {
    const len = product.length;
    sum += product[len - 1]; // Add last number
    productItems.push(product[1]); // Add product name to an array
})

console.log(sum);
console.log(productItems);