Answer:
The word which best completes the sentence is the following one:
him.
Step-by-step explanation:
The sentence is in the imperative mood, which means it expresses a command, and also that the subject is implicit (you). "Him" is the way to go, since it is an object pronoun, not subject, as it is the case of "he". Objects (direct or indirect) appear after the verb, and the same is true here:
Pack some snacks for Connie and him to eat later.
↓ ↓ ↓
Verb direct object indirect object