Hello, Gerri -
Did you purchase the porch swing new or second-hand?
If you purchased it new, then you know where you purchased it (at a bricks and mortar store or online.) You should contact the business or individual seller from which you purchased the porch swing and ask for the needed parts or ask to return the porch swing for a full refund (including the return shipping costs, if you need to ship the swing.)
If you purchased the porch swing second-hand, then you should need to contact the seller about the missing pieces.
Apparently the RUS4172 porch swing is a Living Accents brand. Living Accents appears to be a trademark owned by Ace Hardware, according to Trademarkia:https://www.trademarkia.com/living-accents-77043477.html
You may wish to contact Ace Hardware Customer Service to find out about the availability of the missing porch swing parts:
Toll free phone number: 866-290-5334
24 hours a day
Ace Hardware Contact Us page:http://www.acehardware.com/helpdesk/index.jsp?clickid=footerlink_helpdesk_txt
Note: Your question initially landed in the Fixya.com category of Baby Gear. I recatergorized it to Garden, where questions about porch, yard, and garden furniture seem to fit best.