Learn Dutch: Wij konden geen interessante baan vinden. - We could not find an interesting job.

Kon is the singular form used for I, you, he, she, and it. Because the subject here is wij (we), you have to use the plural simple past form konden.

Why do we use geen instead of niet? Doesn't the English translation say "could not"?

Even though English says "could not find an interesting job", Dutch negates the noun when it is indefinite (meaning it would normally use "een"). Instead of saying niet een, Dutch always uses geen. It is exactly like saying "We could find no interesting job" in English.

Why does interessant get an -e at the end in this sentence?

The word for job is a de-word (de baan). When you put an adjective right before a de-word, it always gets an -e at the end. Therefore, it becomes interessante.

Why is the verb vinden (to find) all the way at the end of the sentence?

This sentence uses the modal verb konden. In Dutch, the conjugated modal verb takes the normal verb position, and the main action verb (vinden) is pushed to the very end of the clause in its full dictionary form.