How do I plug my iPad into my computer

With an iPad with a Lightning socket, with a USB-A to Lightning cable, or a USB-C to Lightning cable.

This cable is often the same cable that is used to charge the iPad.

I'm guessing that you here might have a newer iPad with a USB-C to Lightning cable, and you'll need a computer with a USB-C connection (and which yours probably doesn't have), or you'll need to acquire a USB-A to Lightning cable and use that.

Here's that cable, available in half, one, and two meter lengths:

https://www.apple.com/shop/product/MXLY2AM/A/lightning-to-usb-cable-1-m

For comparison—and so that you can see what a USB-C connector looks like—here's the cable you probably already have, the USB-C to Lightning cable:

https://www.apple.com/shop/product/MX0K2AM/A/usb-c-to-lightning-cable-1-m

Here's the full write-up on this topic from Apple:

Connect iPad and your computer with a cable - Apple Support