I just almost completed PCI scan, which merchant ID?

I just almost completed PCI scan, have 1 question in confirmation page it asks for Merchant ID,
whats that. which merchant ID? my payal id or what.

I do ecommerce

All merchants must establish a Merchant ID (MID) in order to acquire a terminal or establish an online account. Additionally, the Payment Card Industry Data Security Council has established minimum requirements expected of all merchants accepting credit cards. >:-D