@amorse If you're EDU or a business you can get your customer number from ASM or ABM. You may be outta luck though. I'm pretty sure devices need to be purchased from the e-commerce store(ecommerce.apple.com) or through your account manager to get them in DEP.

So in my ABM I have a spot for a number but it's blank. This is what I was hoping to figure out how I get.

I did go to ecommerce.apple.com and tried to request access but my business address isn't in the system and it sent it to another business.....

@mainelysteve The larger Apple resellers such as CDW can also supply orders and serials into DEP.

@amorse Here's how to find your organization's ID that needs to be provided to vendors you're buying Apple equipment from:
1) Click the "Settings" item at the lower-left corner of the screen when legged into the Apple Business Mananger portal
2) Click the "Enrollment Information" item displayed under "Organizational Settings" in the 2nd column of the screen
3) You will see your Organization ID displayed in the 3rd column

You will enter the IDs of the vendors you purchase Apple equipment from under "Customer Numbers" in "Device Management Settings"

@pete_c That's correct. I forgot about CDW. I did get burnt by another slightly smaller education-focused reseller stating they had the ability to add s/n's to ASM but they turned around after my order had been delivered saying to the effect "Uh, no. We never told you that". Good thing it was only 30 iPads.

If you haven't opened the boxes, send them back. Get an account setup with apple first.

Hey Guys, Just to push an update. I called their General sales line and they are getting me the Customer Number. Only way to get it is by calling. Thanks for all the great info!

@mainelysteve , at least with iPads you can use Apple Configurator 2 to enroll them in DEP as well. Just enroll and then let them sit on the shelf for 30 days so that the MDM profile can't be removed.

@RBlount They, unfortunately, were first-gen iPad Mini's. When I first read about that I got all excited then I remembered they wouldn't go past iOS 9.3.5. This was a several years ago now so I'm not particularly worried about it too much anymore.