Is there something like a SD card that can be used with a IPad

The iPad has no slots for SD cards or the like.

Apple makes a Lightning to SD adapter you can use to read and copy photos and videos off of SD cards:

Lightning to SD Card Camera Reader — Apple - Apple

Beyond that, there are external wireless drives that work off SD cards that can be used via their own app with an iPad.

But none of these will offer expanded storage for the iPad. ie no way to store apps on the Sd card or wireless drives, nor access content from the SD card directly via the iPad's native apps, only through the drive's own App.

What exactly are you trying to do?

Lexas has a micro SD card reader that can be used as expandable storage and to transfer files

Lexar MicroSD to Lightning Reader by Office Depot & OfficeMax

I have one and use it with a micro sd card and then usb reader to transfer files to and from the ipad.

You do have to have the lexar app.

I won‘t say it’s 100% flawless because you have to get their app to talk to the app you’re trying to get info to or from, but it does work.

No, but there wireless hard drives intended for iPads.