Where is it written in the Bible that I am wanted? How do I know that I matter to God?
I guess I could start by quoting 1 John 4:8, which says that God is love. But that probably doesn't really answer your question. If God is love, then he loves all of his creation, but how do you know that he loves you.
The next verses after that one, though, show that God loves you, wants you, thinks you matter. "Herein was the love of God manifested in us, that God has sent his only begotten Son into the world that we might live through him. Herein is love, not that we loved God, but that he loved us, and sent his Son to be the covering for our sins."
Paul explained in Romans 5:6-8 that God loves each of us so much (loves you so much) that he did what we find almost incomprehensible-he let his son die so that we/you might have eternal life. "For while we were yet weak, at the proper time Christ died for the ungodly. One would hardly die for a righteous man; perhaps someone would dare to die for a good man. But God commends his own love toward us, in that, while we were still sinners, Christ died for us."
God is so righteous that he cannot abide the presence of sin. We all sin, so cannot come into the presence of God. After Adam's sin, God could simply have written off the whole of mankind. Instead, even before the creation he had planned a way to bring man back into a state in which he could come into God's presence. God loves each of us so much that he was willing to sacrifice his only begotten son in order that each of us could come back to God.
How do I know that that is true for you as well as me? Peter says that God is "not willing that any should perish, but that all should come to repentance." (2 Peter 3:9)
Some people might ask, "Then why did he make Hell for people?" He didn't. Matthew 25:41 says it was prepared for the devil and his angels. Those who don't turn back to God and obey him may be punished there, but it was never God's intent that man should go there. Instead he wants all to be with him. That won't happen because God gives us a choice, but that is what he wants.
The problem I have in accepting Calvinist doctrine as held by some Presbyterians and Baptists (and as is taught in Islam) is that the doctrine of election says that God loves some people and chooses that others have no chance of salvation. They imply that there are some people that God does not want, who don't matter to God. What I learn in the Bible is that God gives us free will, that we can choose not to live with God, but that God wants all of us to choose him.
Finally, one of the most familiar passages in the New Testament says God loves you. John comments on something Jesus told a man named Nicodemus. "For God so loved the world that he gave his only begotten son, that whosoever believeth on him should not perish, but have everlasting life." (John 3:16)