What are dimensions of square acre in feet?

We have to be careful here. First, I want to be sure that you know that there's
no such thing as a "square acre".

"Acre" is a unit of area, specifically, 43,560 square feet of area, or 4,840 square yards.

The acre can be any shape at all, with any combination of dimensions at all, just
as long as it encloses that much area.

Now, you're asking: "If the acre happens to be square, what are its dimensions ?"

The answer is: the square root of (43,560 square feet) = 208.71 feet on each side. (rounded)