All thy land which is within thy borders; a synecdoche; so that word is used also Exodus 10:4,19 1 Kings 1:3 Psalms 147:14 Jeremiah 15:13. So the gate and the wall are put for the city to which they belong, Genesis 22:17 Amos 1:7,10,14.
Related Commentaries of Exodus 8:2
Exodus 8:2
2 And if thou refuse to let them go, behold, I will smite all thy borders with frogs: