New MBP -> iMac Target Display / TB3 -> TB1 cable? Or...

[jackoatmon]

Hey so I ordered a new MBP.

I wanna use my 2011 27 inch iMac as a second screen sometimes. Is there a single cable that can enable this? I've never used the Target Display feature before.

 

[Floris]

https://support.apple.com/en-us/HT204592
I hope that helps.
You probably need the t3->t* adapter