Hello dottytot, welcome to Stamp Community!

You could look on
ebay, searchig for 'olympic' or 'olympiad' and then the year or / and the country (in English), to see what others are selling their's for.
Sometimes selling one set of stamps at a time or even one stamp at a time gives you bigger returns.
The Olympics is a big collecting topic and very popular, and sometimes even certain sports or events are wanted, or flags, famous people, scenes, etc.
But also keep in mind that during the Olympics many countries issue a lot of stamps to sell to collectors, so some are valued more than others, depending on the topic and rarity or lack of.
A Scott's Standard Catalogue of Posage Stamps, multi-volume (6-7 now) printing, that is in colour now and lists stamps by their issue date and country, would be a nice reference to have. Usually found in most libraries in the loan-out section and the reference section also.
There are even probably separate catalogues for certain popular topics like the Olympics.
The American Topical Association (ATA) has lists of stamps in topic collecting areas.
Sold as a group, most stamps will go for very few cents each. Sold singly or in sets to the right collector at the right time (say a stamp show or bourse or even a stamp club meeting or
ebay over time) you will have a better chance of getting a fair price.
Retail price is difficult to get unless they are rare or really wanted in a collection. Collectors are picky sometimes.