C.O.
Never a stupid question!!
If your post office is a full service post office, you can get boxes, tape, envelopes, etc. there.
We have two post offices - one satellite one that accepts packages and has stamps and the post office "free" boxes.
Our main post office has it all - cards, stamps, shotkies (spelling), boxes, padded envelopes, envelopes with postage already on them...can you call them to find out if they are full service?