* Nosotros buscamos nuestros regalos de Navidad, pero no estaban en la casa.
Explanation:
Because the tense peterito is used to express actions carried out in the past tense and that have not yet defined their end, therefore it is important to identify the person, gender and number in the sentence so that we can conjugate the verb correctly and that it has agreement with what is being expressed.
It would be "llegaron". A really helpful tool is to look at some online tables that share regular conjugations for the preterite tense. Hope this helps!
