electrical adaptor/converter

Get a simple plug adapter - you don't need anything fancy like a "converter" for charging a camera or phone - all modern phone and camera charges are dual voltage. (though if you want to be sure, check the specs on the power adapter you are using - in small print, if it says 110v-240v or something like that, you are good).

I have a couple of plug adapters that work in most European countries. They are maybe $2-$3 USD on Amazon or eBay.

Here's an example for $3.99 on Amazon:

www.amazon.com/gp/product/B01C5TG278

All USB chargers convert to 5 volts out.

You may want to get one with a decent amperage (over 3 amps) to handle tablets too.

Other than that, you’re good.

If you use a US USB charger you’ll need a plug adapter.

They also sell the plug adaptors at Wal-Mart , very inexpensive.
I use it all the time while traveling to charge my camera battery.

We always travel with 3 or 4 plug adapters; they are easy to lose or leave behind and it is a lot easier to buy them in the US of course than in Europe.

Along with a cheap plug adapter, I usually travel with a short (6') extension cord with 3 outlets at the end. This way, with one adapter, I can charge my laptop, phone, flash battery, etc. Plus, sometimes the actual outlet in a hotel room is in an inconvenient location. The 2 meter cord brings my devices to a more convenient location.

luis,

As mentioned in previous replies, you must check the "Input Voltage" ratings on the chargers to ensure that they're designed for operation from 100-240 VAC. Most modern electronics are designed for "world operation" so it's likely your chargers will have that capability, so you won't need a "Converter".

As you posted this question in the France section, I assume you're only traveling to France? If that's the case, then you'll need THIS Plug Adaptor for ungrounded (two pin) appliances. I'd suggest packing along a couple as they're easily misplaced.

The two-prong adapters seen in the links above do not provide a ground. New or modernized hotels will likely have a more intricate plug receptacle. The ground protrudes from the receptacle and may be too snug for a two-pronged plug to slip past. The modern adapter still has two plugs but also a hole to accept the ground. https://www.amazon.com/dp/B0098B5GN8/ref=psdc_10967761_t3_B01C5TG278

Given how cheap these adapters are on the Internet, you could take one of each. I like the suggestion about an extension cord, after clawing around under beds to find the only available plug box.
The "universal" adapters sold at bargain prices deserve a bit of caution for countries away from France. These things often have a third prong that folds down -- but it is plastic, no use whatsoever as a ground.