Migration issue from iMac partition to MacBook Pro

I had created a Partition on my iMac for Sierra OS to test Sierra OS with my apps before buying the new MacBook Pro laptop.

I can't get rid of my El Capital partition now on my iMac. (Another story). I fubarred my time machine backup, erased the content on my El Capitan volume (hoping to delete it, which I can't). I've tried restarting with a recovery volume. That doesn't work either.

Setting those issues aside, how can I use my iMac Sierra partition/startup disk with migration assistant to my new MacBook Pro. I get an option to only migrate my entire iMac, for which I get an error on the MacBook Pro saying there is not enough room. I don't see an option to migrate from my Sierra startup disk which I have booted from to start my iMac.

I'm using the network connection for migration.

 

I don't get that screen.

 

I looked at "about this Mac" on the MacBook Pro. Under Storage it says for the Macintosh HD I have 229.65 GB available out of 249.68.

The hard drive icon shows a caption:
251 GB
Flash Storage

--- Post Merged, Aug 13, 2017 ---

I only get Applications
Documents & Data (edit)
Computer and Network Settings as choices

I chose my account from Edit
and unmarked Applcation and Computer and Network settings

I assume there is not enough room b/c the system hard drive is messed up.
I just bought the machine and backed it up to my external hard drive that had time capsule backups from my iMac on it. Maybe that's related to my problem? ( i can't get any backups off my external hard drives now from my iMac.)