Hi there!
»»————- ★ ————-««
I believe your answer is:
[tex]2\sqrt{7}\text{ } in.[/tex]
»»————- ★ ————-««
Here’s why:
[tex]\rule{150}{0.5}\\$\bullet \text{ Area of a square is: } a^2\\\text{ } \rightarrow a - \text{given side}\\\rule{150}{0.5}\\a = \sqrt{28}\\\\\rightarrow 28 \text{ can be factored to } 2 * 2 * 7\\\\\rightarrow\sqrt{28}\\\\\rightarrow \sqrt{2*2*7}\\\\\rightarrow \boxed{2\sqrt{7}}\\\rule{150}{0.5}[/tex]
»»————- ★ ————-««
Hope this helps you. I apologize if it’s incorrect.