How do I copy a value from one spreadsheet to another within iCloud Numbers?

In iCloud Numbers I created a Table "A" with a spreadsheet "2016 Cat", and spreadsheet "Details".

I want to copy the value in Details B15 into B26 of 2016 Cat B26.

I tried:

=Details::B15 --- (didn't work)

I am on B26 2016 Cat spreadsheet. press = (then I went into Details B15) press enter --- (didn't work)

Please help

May