Sometimes, to confirm your Merchant Token (also known as Merchant ID or Seller ID) for security purposes. Here's how to find it!
Log in to Seller Central as the primary user.
Hover over the Settings gear in the upper-right corner and select Account Info from the dropdown menu.
Click Business Information on the right, then click Your Merchant Token.
That will open the page displaying the Merchant Token.
Click Copy next to the Merchant Token you need copy it.