Images in SD card show up on the iPad but I can’t delete them

Could you delete them in the past on the iPad? If so, the little toggle (slider) on the side of the SD card could be in the locked position and all you have to do is move it the other way to unlock the card. This way you can delete on any computer or otherwise.

When you say reformat on the camera, are you meaning iPad camera or regular digital camera. My regular camera has a setting in its setting for that. Don’t thing iPad does.

While file deletion from connected SD and USB storage is possible using your iPad alone, should formatting and/or partitioning of external storage devices ever be required, this must be performed using a separate computer - such as a Windows PC or Mac computer. iPad does not provide any facility to format an external storage device.

SD cards are best formatted by the camera with which the card will be used.

To be recognised by iPadOS, the attached storage device must be formatted to FAT, FAT32, exFAT, APFS or HFS+ with a single partition. Microsoft NTFS and other proprietary device formatting are not supported. 

More information about connection to external devices and storage can be found in the iPad User Guide - along with other frequently overlooked information about your iPad and iPadOS:

Connect external storage devices to iPad - Apple Support

One other thing that I read. I was having trouble getting my printer/scanner reading my card. I searched and searched and found an article that said... Move the SD Lock/unlock slider to the half way position then insert. I did and It worked, then I could do all I wanted to do.

You can try this too.

Great!