"Here are the pants I ordered."
Translation:Voici les pantalons que j'ai commandés.
ce only means "that" when it is used as a demonstrative adjective as in "ce garçon" → that boy. le is either the masculine definite article meaning "the" or the masc. direct object meaning "it" or "he".
However, "that" here is a relative pronoun that is usually left out of English sentences.
"Here are the pants" point 1, "that" (the relative pronoun) "I ordered" point 2. The 2 points are related but the French sentence requires the relative pronoun "que".
do you make the past participle plural if the pants are plural? i thought it was only with the être verbs that you change the past participle according to gender and singular/plural?