If you don't need to back up the trailer at any point, then you could try and get away with using a 4-pin "in a pinch." But if you do need to back the trailer up, that 5th pin is needed to electronically disengage the surge brakes when you put the vehicle in reverse, otherwise the trailer will be working against you as you try to back it up.
Some trailers with surge brakes come with a brake lockout bracket (also called a "chuck") that you can insert behind the roller pin to keep it from moving when backing up the trailer.
Some surge brake systems have a brake lockout cap that lets you manually disengage the brake so you can back up the trailer without the trailer's brakes engaging.
If you have either option, you may not need a 5-pin adapter for a short trip. However, a 7-blade to 5-pin adapter is not expensive. You can use a 5-pin adapter on a 4-pin trailer (you just keep one hole empty) but you really can't use a 4-pin adapter to support a 5-pin trailer without it affecting the trailer's functionality.