USB C or USB 3.0 Hard Drive?

Wanted to buy a LaCie (External Drive), but I don't know if I should buy it with USB C or USB 3.0.

Does that make a difference to the side you put in the laptop? My last USB stick was 3.0, does USB C automatically fit? Which one is recommended?

They don't have the same function, USB 3.0 is better

But would both connectors fit in the computer?

These are different connector types, look here

Take the one that fits, in your case USB 3.0 (new laptops also have a USB C port, you had to have a look)

Otherwise you are on the safe side with USB 3.0.

3.0 is the generation name, higher numbers equal faster, but they are compatible with each other, so no problem.

The letters A B C have different shapes and only fit on the counterpart, so you have to be careful

No, left my comment

USB3.0 is initially only a standard, mostly used but with connector type A (the big, "normal")

USB-C is a connector type (the small round, non-rotating)

Although USB-C is newer, it doesn't have to mean that it also achieves USB3.0 speed.
Unfortunately, there are even USB-C cables that only have USB2.0.

A reasonable product with USB-C will normally also have the latest USB standard