It's not that easy because the original document is quite unstructured (not using a hierarchical layout, but a flat one), but here is how you can extract the main text fields with the Html Agility Pack:

        HtmlDocument doc = new HtmlDocument();
        doc.Load("yourDoc.Htm");

        // Get A nodes that have an HREF attribute
        foreach (HtmlNode node in doc.DocumentNode.SelectNodes("//b/a[@href]"))
        {
            // This will contain anchor's displayed text
            string title = node.InnerText;
            Console.WriteLine("title=" + title);

            // Get the 1st BR, and then it's next sibling of TEXT type.
            HtmlNode sizeNode = node.SelectSingleNode("../following-sibling::br[1]/following-sibling::text()");
            Console.WriteLine(" size=" + sizeNode.InnerText.Trim());

            // Get the 3nd BR, and then it's next sibling of TEXT type.
            HtmlNode eanNode = node.SelectSingleNode("../following-sibling::br[2]/following-sibling::text()");
            Console.WriteLine(" ean=" + eanNode.InnerText.Trim());

            // Get the 3rd BR, and then it's next sibling of TEXT type.
            HtmlNode upcNode = node.SelectSingleNode("../following-sibling::br[3]/following-sibling::text()");
            Console.WriteLine(" upc=" + upcNode.InnerText.Trim());
        }

This will display:

title=Peanut Delight Peanut Butter & Grape Jelly
 size=Size: 18 oz
 ean=GTIN/EAN-13: 0041498143909 / 00-41498-14390-9
 upc=UPC-A: 041498143909 / 04149814390
title=Nabisco Nutter Butter Sandwich Cookie Bites Peanut Butter
 size=Size: 10 oz
 ean=GTIN/EAN-13: 0044000046118 / 00-44000-04611-8
 upc=UPC-A: 044000046118 / 04400004611
title=Nabisco Nutter Butter Sandwich Cookies Chocolate Peanut Butter 4 Ct
 size=Size: 12 oz
 ean=GTIN/EAN-13: 0044000003562 / 00-44000-00356-2
 upc=UPC-A: 044000003562 / 04400000356

etc...

NOTE: It's not 100% finished, as you'll have to parse the size, ean and upc variable using standard string manipulation (IndexOf, Substring, etc...) or Regex but the Html side of things is done.