Which dock connector fits an iPod touch for charging and audio?

Pin? What do you mean by "what pin"?

The Dock Connector is what Apple Called their older 30 pin connection on iPods, iPhones and iPads.

If your speaker has a 30 pin connector on it, and have an iPod touch with that type of connector, then you should not need anything and you can connect the iPod directly to it.

If your iPod touch is a newer model, like the 5th, 6th or 7th generation then it has a Lightning connector. If your speaker has a 30 pin connector, then you'll need an adapter to go from 30 pin to Lighting.

click here ➜ 30 pin to Lightning Adapter - Amazon.com

Most speakers will simply use the 3.5mm headphone jack connector for audio these days rather than some special connector type while charging would use the other connector on the iPod.

What you need will depend on what devices are involved exactly.

click here ➜ Identify your iPod model - Apple Support

Since you have an iPod Touch, you have an audio jack. All you would need would be a cable to go from your iPod to the speaker and another to connect to power.

If you're looking for a physical dock that you clip your iPod into, that's a harder task. I have a speaker that my iPod plugs into, but only the audio jack. The power is a separate cable that is used. Which is handy in that it it worked with my iPod Touch v3 which had the 30-pin connector and works with my iPod Touch v7 which has the lightning connector.