How did the location of Constantinople help it grow wealthy and prosperous?

Answer 1

What does your text say? I'm sure the answer is there, if you read them. You'll find lots of information among these articles, too.

https://www.google.com/search?q=constantinople+as+trading+center&ie=&oe=

Answer 2

Constantinople, formerly Byzantium, is now called Istanbul. It's on the border between Europe and Asia. It also is directly between the Mediterranean and Black Seas.

https://thehistoryofbyzantium.com/maps/