みなければ

if (someone) doesn't look/see

→ 見る
see, watch, look at + なければ Negative conditional (“if not”)
auxiliary · conditional Rare #34,550
if (someone) doesn't look/see The conditional form of 見る with a negative meaning; often translated as “unless someone looks/sees.”
JA: よくみなければ、違いが分かりません。
EN: If you don't look carefully, you won't understand the difference.
Conjugation of 見る
Conditional
みたらみればみなければ

捜査が終わってみなければ事実は分からないだろう

We won't know the truth until the investigation is complete.

— Article 15 (2019)

私たちはその計画を良く考えてみなければならない

We need to think the plan through carefully.

を買う前に試しに履いてみなければならない

Before buying shoes, you have to try them on.

試してみなければ決して分からないだろう

You’ll never know unless you try.

やってみなければ自分の力わからない

You won't know what you're capable of until you try.