Max value of a field and its coordinates

Hello,

I know that there have been a lot of posts about this topic and I have read many of them but I am still as dumb as before.

I need to find the value of the maximum value of the field in a domain and its r and z coordinates.
I defined a maxop1 operator in model definitions. I then go to the results/derived values and find the value of maxop1(mf.Br,r). It gives me a value which I think is the value of the r-coordinate. However it does not say anything about its value which is what I primarily am interested in.

So i still cannot find out how to calculate the masimum field as well as its r and z coordinates.

Please tell me in a way that I can understand how to do this.

Thanks for any help.
Kamil