God is our Creator. Because he is our Creator, we are existing for the purpose of God. It is because of His purpose that we were created. We would not have been created if God did not have the purpose for our creation. There is no other purpose for which we are created than the purpose of God. We were made to fulfill the glory of God. God has the reason for our creation.
When we consider our existence in the light of God's purpose, it will be clear to us that we were conceived and created for the purpose of God alone. We were designed for the purpose of God. We are in this world to fulfill God’s purpose.
God did not just created us, he prepared a conducive home for us. He prepared everything existing in order to help us to do His purpose. So, we are only existing because of the purpose of our Creator.
Yes dear, our Existence on Earth is mainly to serve his purpose for creating us, every other things comes after