If you used a new digital camera then follow it's instructions to transfer the digital picture onto your hard disk. You can find places to scan your prints for a nominal charge or you can buy a scanner and scan them yourself. Now you have a digital picture on your hard drive or a diskette. A word of caution. Even the .jpg format can be quite large.
Large files take a long time to send by e-mail.
There is plenty of free software to allow you to reduce the size of those files, at the expense of some picture quality, so consider doing that to save not only transmission time but the amount of disk space required to hold the pictures. When you download a file from the Internet you usually get a dialog box to specify where you want the file to be placed. Files downloaded from the Internet may be large files. Your diskettes hold relatively small amounts of data. You can do a calculation to see how many diskettes you will need for a particular download file size.