Philippians 4:6 NKJV - "...let your requests be made known to God."
"If God already knows my needs, why do I have to tell Him what they are?" This is one of those questions almost every Christian will ponder at one time or another. There are a few answers that you might find helpful.
First, being specific with your prayer requests is good for you to trust God for something specific. It's better than praying, "Please God, bless me today." It's not wrong to be general, but God loves it when we lay before Him the requests of our hearts in a very detailed way.
Second, when the request(s) is answered then you can be thankful for the specific answer to the specific request. It's great when you can clearly see God working "in the details!" Again, it's okay to be thankful for general blessings if that's all you're looking for.
Third, being specific with your requests is learning to trust that God really hears you and is aware of the exact nature of your need. He wants you to grow in your faith, and that means trusting Him for specific answers to specific needs in your life. This encourages you to pray again, especially when another specific need arises.
Fourth, bringing your requests to God helps you to make sure you understand what you're specifically asking of the Lord. In a way it's not God who needs to learn what your requests are. You need to learn that! Doing so you can get a better picture of your "need" and determine whether it's what you really need. Sometimes when you're praying God will help you recognize that you may be asking for one thing when you should be praying about something else, or that you're asking for something that you don't really need at the moment.
God isn't trying to make prayer hard for us. But then neither is He accepting the feeble and casual ways many Christians approach Him in prayer. He wants serious praying from serious believers who recognize that God is serious about answering our prayers.