At a minimum you will need an adapter. If your equipment (particularly battery charger) doesn't accept 220V you will also need a transformer. If your equipment can't accept 50 Hz (vice US 60 Hz) you can't plug in.
If you get your boat set up for Europe you will be fine in the Azores.
I recall availability of 16A 220V 50Hz at all the slips. I don't remember it being available on the bulkhead but I was rafted out until a slip was available so I may have simply not noticed. I don't remember seeing 30A outlets but I wasn't looking.
You can buy small transformers at Mid-Atlantic Yacht Services in Horta but they are limited. If you really have a 50A boat I would consider sourcing a built-in transformer before you leave and buying the appropriate pigtails in Horta. Even so you may find yourself a bit more limited in the Azores and Europe than when at the dock in the US.
It will be cheaper in the US to boot. While most are hardwired, you might be able to find one that can simply be plugged in-line. Better yet, build a waterproof box that can house the transformer with appropriate connectors for AC in and out.
Marinco makes an adapter from 30A US to 16A Euro. It wasn't easy to find and I expect you'll have to order it. You might have best luck engaging MAYS ( [email protected] ) ahead of time - they may be able to have it for you when you arrive if you can't find it in the US. Perhaps there is a 50US - 16Euro or 50US - 30Euro adapter as well? Sorry - I'm not as familiar with that stuff as the 30s.
I used a garden variety tool transformer (the sort that MAYS sells) in the UK and Azores. It was rated at 10A continuous (20A on the 120V side). I adjusted my battery charger so it would not draw too much and switched off the water heater. Other AC loads are just incidental chargers for phones and such. My water heater is pretty well insulated so by switching off the battery charger for a few hours each day and turning on the water heater there was hot water for a day or so.
Have you read Jack Tyler's information on cruising Europe? I recommend it highly. Whoosh
In addition to electrics, spend some time thinking about water. I have ended up with a small bag of adapters and a pre-filter that have served me well. Read Jack's bit on water. I found some very useful adapters at Home Depot and Lowes that connect US-spec hoses to garden soaker hose that work well for Euro-dock hoses (which often have no termination on them at all). If you get a pre-filter (which I am pleased to have) I suggest a practice of disassembly to dry the cartridge after each use to avoid nasty growth. I soak mine in vinegar after use before drying for storage. YMMV.