The key here is to not worry too much and just follow PEMDAS.
Here we have the expression [tex](5\cdot 7)^2[/tex]. Following PEMDAS, we complete the expression inside the parentheses first, or [tex]5\cdot 7 = 35[/tex]. This gives us [tex](35)^2[/tex] or just [tex]35^2.[/tex]
Hope this helps.