Will I need a converter? Or a plug adaptor?
Plug adapter.
You'll need a plug adaptor. If you plan to travel a lot in the future, Apple sells (or used to sell) a set of converters that worked all around the world. If not, just look for the adaptor for the country which you're visiting.
joan,
You'll need the Euro Plug Adapter with two round pins - https://www.amazon.com/Ckitze-EU-10PK-European-Adapter-Converter/dp/B0012IY41U/ref=sr_1_19?ie=UTF8&qid=1542176670&sr=8-19&keywords=euro+plug+adaptor
I'd suggest packing along a couple as they're small and easily misplaced.
Adapter is all you need for iPhone or iPad. I second Ken's suggestion to take at least 2. Easily misplaced and left behind.
If you live in the USA, any store like Best Buy, Target, or electronic store will have adaptors for Europe. You just plug your charger into it.
Happy Travels✨💫
I always take several plug adaptors along.