What type of plug or converter I need to charge my iPhone 12 Pro Max in Spain?

You will find the plugs (C and F) used in Spain here:

https://www.iec.ch/world-plugs

The local voltage is 230 V AC and the frequency 50 Hz according to this web page.

You may be able to use an existing power adapter (charger) via an appropriate passive plug adapter. Apple power adapters typically have an input voltage range 100-240 V AC at 50 to 60 Hz. Third-party power adapters may be more limited. Look for a text/label (a magnifying glass may help) with voltage and frequency data. It is good practice to check this before connecting anything to the mains in a foreign country.

’m traveling to Spain and wondering what type of plug or converter I need to be able to charge my iPhone 12 Pro Max

Will you be using an Apple "charger"?

If yes, all you will need is a Type F wall adapter. Amazon has them:

https://www.amazon.com/Grounded-Universal-Schuko-Adapter-Germany/dp/B004SY5O5K?th=1

You will probably need 4-5 adapters to handle a few iPhones, a laptop, the razor, hairdryer, toothbrush, etc. Make sure that the devices will operate on 100-240 Volts.

You'll need an European power brick, a travel socket might do the trick