Breakdown of Я смотрю на печать, которую вы ищете.
я
I
вы
you (plural)
на
on, at / by (transport) / to (a place) / to (in answer to)
смотреть
to watch / to look at / make sure (in a warning)
Questions & Answers about Я смотрю на печать, которую вы ищете.
Why is the word for "which" in the form которую?
The relative pronoun который acts like an adjective, so it must match the gender of the noun it refers back to (печать, which is feminine). It takes the Accusative case here because it is the direct object of the verb in the second half of the sentence: you are looking for "which".
How do I know печать is feminine, and why didn't its ending change after на?
Nouns ending in a soft sign (-ь) can be masculine or feminine, and you generally just have to memorize their gender. Печать (seal/stamp) happens to be feminine. After the preposition на (meaning "at" here), we use the Accusative case. For all feminine nouns ending in a soft sign, the Accusative form is identical to the Nominative dictionary form, so it doesn't change.
I see the verb ищете means "are looking for", but what is the infinitive form?
The infinitive is искать (to look for / to search). It belongs to a common group of Russian verbs that undergo a consonant mutation in the present tense. Here, the ск changes to щ, giving us forms like я ищу, ты ищешь, and вы ищете.
Why does "look at" use the preposition на (смотрю на), but "look for" (ищете) has no preposition?