13 הִנְנִי (hinni) before the active participle מֵבִיא (mevi’) is the imminent future construction: “I am about to bring” or “I am going to bring”—precisely, “here I am bringing.”
14 One of the words for “locusts” in the Bible is אַרְבֶּה (’arbeh), which comes from רָבָה (ravah, “to be much, many”). It was used for locusts because of their immense numbers.
15 Heb “within your border.”

In other versions

For if you refuse to let my people go, behold, tomorrow I will bring locusts into your country,

If you refuse to let them go, I will bring locusts into your country tomorrow.

But if you refuse to let my people go, then tomorrow I will bring locusts into your territory.

If you refuse, watch out! For tomorrow I will bring a swarm of locusts on your country.

But if you are refusing to release my people, look, I am about to bring locusts into your territory tomorrow.

Else, if thou refuse to let my people go, behold, to morrow will I bring the locusts into thy coast:

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