Mi abuela nos cocina la paella.
In the original sentence "para nosotros" is a prepositional phrase that functions as an indirect object. To replace it with a direct object pronoun, we need to use the pronoun "nos" which means "us" and place it before the verb "cocina". This results in the sentence "Mi abuela nos cocina la paella", where "nos" is the direct object pronoun that replaces the indirect object "para nosotros".