You have an old coach and equipment wasn't nearly as standardized as it is today, so we are just guessing until you can identify the coach equipment better. However, odds are strong that it was a 30A power cord, a 3" Valterra-type sewer connection, and a standard garden hose connection for fresh water. It's the sewer line connection that was most often different back in the day, so a photo of it would help.
If the plug on the power cord looks like the one below, you have 30A RV shore power and probably won't need any adapter anywhere you go.
https://www.walmart.com/ip/Camco-RV-30-Amp-PowerGrip-Replacement-Plug/29764595
If you want to plug into a standard 15A wall outlet, e.g. at home, get a 30A-->15A adapter at Walmart - they have an RV section with common accessories.