One neat thing about prayers is that they can be literally any length. Of course, you can pray for as long as you want about anything you want to pray about, and that can make your prayer as long as you need it to be, but shorter prayers are also valid. It's nice to include the niceties of "Dear Heavenly Father" and "In the name of Jesus Christ, Amen," but these can be abbreviated, or even eliminated. Perhaps it's good to start a prayer of thanks with "My dear, kind, loving Heavenly Father, I thank thee for..." and then list every blessing you've ever received, and close with "in the name of my Savior and Redeemer, Jesus Christ. Amen," but it's also good to periodically look up toward heaven and just say a heartfelt "Thanks." Honestly, I'm sure we don't even need words at all. You can send your thoughts to God, and He'll hear them and understand them as clearly as though you had said them all out loud.
We can say prayers with dozens, or perhaps even hundreds of words in them, if we feel the need to, but we can also "say" prayers using no words at all. The lengths of our prayers can be whatever we want or need them to be, whether that's exceptionally long or infinitely short. I'm sure God is just glad to hear from us, however what length our prayers are.