Parvo is a disease mostly affecting puppies. In general, most dogs who contract parvo are younger then 1 year of age though dogs older then one can still get the virus. Dogs that are around three years of age can become infected with parvo, especially if they have never had any vaccines to protect them against Parvo.
The good thing is that, if you are unsure whether your dog got vaccinated against parvo, you can give your vet a quick call and they should be able to tell you. When your dog was vaccinated, they keep it on record along with other info such as lot numbers, batch and when it expires. The parvo shot is a core vaccine and one of the most frequently given, most likely if your dog received shots it was included, but always best to check to play it safe.