I have a mini R56, the passenger side, it's the black line that's right behind the window vertically. Not the chrome at the bottom since that's the only thing that comes up when I've tried looking it up. I hope someone can help because it's not there but the residue is there so if anyone can also help to remove that, I'm going to read a sticky that I saw about wax residue and I hope that answers it but if it doesn't pls help :p
thanks and sorry if this isnt allowed here.

 

I found the piece, I'm just trying to find out how to delete this post now Haha sorry

 

Instead of deleting the post why don't you tell us where you found it so that somebody else with the same question will have that information.

 

That's a great idea!
Well for anyone looking,
It's called the "B Pillar" on either the right or left side. I found the part number for my exact mini but for reference it's just called the B pillar. Its number 10 on the picture shown below.