I would buy two 10-ft hoses. Get good supple ones. The cheap hoses get brittle too fast and crack. Also get caps for the hose ends to reduce messes and smells.
As @Binghi said, two 10 ft hoses are a good choice. You'll also need an elbow for the connection at the campsite. Either of these kits contain the key pieces. There are several other similar choices.
Might want to consider getting a dedicated water hose for the black tank flush connection. It probably wouldn't seem too obvious until you use a dump station.
Comments
https://www.amazon.com/dp/B01HPHR30U/ref=sspa_dk_hqp_detail_aax_0?sp_csd=d2lkZ2V0TmFtZT1zcF9ocXBfc2hhcmVk&th=1
https://www.amazon.com/dp/B00BDEPJ1W?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_7&th=1
You will need a clear, 90 degree bend. Without the clear section, you won't know when it's done.
"Just Enough"