I need to download photos from iPad, to Microsoft Windows
When you say stored in iCloud do you mean the iCloud Photo Library? If this is the case you can go to Settings - iCloud - Photos and switch from Optimize Storage to Download and Keep Originals to download full copies of your photos back to the device. Turning off iCloud Photo Library will also give you this option. 

And as was also mentioned you can also log in at iCloud.com and get them from there. 

ETA: there's also the iCloud for Windows option.