Question

Suppose abc and def are three-digit numbers such that
(abc+def)square=abcdef.
Find abc

abc means 100a+10b+1c, as opposed to a×b×c. As an explicit example, for a=2,b=3,c=4, abc=234 and not 2×3×4=24.

The number 12=012 is a 2-digit number, not a 3-digit number.