piracy era

Let's say this is around 1650 to 1730 so we get both the caribbean buccaneers and the rise of piracy that followed the end of the wars of spanish succession.

I wonder how many crews ships in piracy era have?

Depends on the ship of course, let's stick to the Royal Navy rating system so we have some kind of basis for what the different ships are.

A very large first rate ship of the line could have complements upwards of 900 men. These are giant three gundeck ships, almost floating fortresses. Consequently a small cutter can be handled by a single person (although for the purpose of war some 20+ people are usually required to do something relevant like pilot a large enough cutter and man a few guns). So a warship would have anywhere between 900 and 20 people on board although the smallest blue water warships were mostly large enough to carry a complement of at least 100.

how can we list warships as size and

The rating system uses the number of guns as a measure of what kind of warship it is. Size and complement usually follows the number of guns pretty well for ships of the line.

How many people does it take to operate a historical sailing ship?

Minimal? Again, this depends on the ship and conditions but most large sailing ships can be managed with a handful of people. It will not be fast, you won't be equipped to handle hard weather and it's a lot of work but it can be done. Naturally this is just for the purpose of moving a vessel from point A to point B, not fighting.

What type of ships does barbary pirates uses.

Again, this depends on time period and purpose but galleys and smaller ships were common however the use of captured ships was not uncommon, especially among European born "turks" like Zymen Danseker or Jack Ward.