Your iPad only supports wireless printing, either directly to the AirPrint enabled printer, or through a computer software, or an app from App Store. Connecting a printer to it with an USB cable won't work.
Afaik a USB stick has to be formatted in a certain way to be recognized by your device. I don't know if it's possible to transfer photos to it from your iPad.
There are several other options you have:
You could save your photos to online storage such as Dropbox, SkyDrive, Google Drive, Sugar Sync, Box, ..., set those up on your computer as well and print from your computer.
You have the possibility to connect your iPad wirelessly to something like the Apotop Wi-Reader, and use the app that belongs to it to transfer your pictures to an USB stick.
If you only need to print a few photos, you can send them to yourself via email, open the email on your computer and print from there.
There certainly are other options as well that I'm not aware of.