Precious metals like silver are measured in Troy ounces which is different from Avoidupois ounces used to weigh food. I might suggest taking your silver in bags and asking your grocer if you could weigh it on your scale. Then covert to Troy ounces on one of the free Internet scale conversion programs. This will give you the weight in sterling silver which is 92.5% silver and 7.5% copper.
Spot price is what the stock market or world market says the metal is worth that day. Currently the spot price of silver is about $10.50 per ounce. The Internet is a good source for silver spot price.