How can I copy photos on my PC to Photos on my iPad?

To synchronise or transfer files or photos directly between iPad and a Windows PC, you might choose to to install iTunes for Windows:

Download and use iTunes for Windows – Apple Support

Update to the latest version of iTunes – Apple Support

Alternatively, you might consider using iCloud for Windows. When signed-in with the same AppleID, you can simply use iCloud to exchange or synchronise files:

iCloud for Windows

Download iCloud for Windows – Apple Support

Set up and use iCloud for Windows – Apple Support

You can install and use both on the PC. They will happily coexist - and provide considerable flexibility in how you move/share/transfer photos and other documents and data between iPad, iPhone and your PC.

You might also consider copying/moving files using USB storage. For an iPad with a Lightning connector, you’ll require an Apple Lightning to USB3 Camera Adapter:

https://store.apple.com/uk/xc/product/MK0W2ZM/A

try reading

Sync photos between your Windows computer and iPhone, iPad, or iPod - Apple Support