Susan, If you sync your iPhone and iPad with your new iTunes Library (and iPhoto Library), everything on your iPhone and iPad will be replaced with the new iTunes Library (and iPhoto Library). So before syncing the iPhone and iPad, you must transfer the photos from your old PC to your iPhoto Library.
You can copy the photos to a USB Flash Drive, then copy them to your Mac and then import them to iPhoto (via File menu > Import)
If you don't have the photos on your old PC, then you have to use third party applications like ImToo iPad Computer Transfer for Mac (click here) to transfer the photos from your iPhone or iPad to your Mac, then import those transferred photos to iPhoto.
After importing the photos to your iPhoto Library, follow the steps below to sync your Mac with iPhone and iPad (one time setup)
- Open iTunes from Applications folder.
- Connect your iPhone or iPad to your Mac with the USB Cable.
- In iTunes, select your iPhone or iPad in the top right
- Click Photos tab next to Summary, Apps, Musics etc tabs.
- Enable "Sync Photos" option and make sure iPhoto Library is selected there
- Click Apply or Sync button in the bottom
From now on, your iPhone and iPad will be synced with your iTunes and iPhoto Library.
If you want to sync new photos or any new contents, all you have to do is open iTunes and just connect your iPhone or iPad. It will be synced automatically.
You can do the same for Musics, Apps etc (For Musics, enable "Sync Musics" option under Musics tab etc)
Note : You have to sync everything through iTunes application
Please let me know if that didn't work, so we can continue troubleshooting.