You can, though depending on the age of the fonts and your newer printer, they may not look as good as they could. If you’re moving fonts from an OS 9 Mac, they’re probably old Bitmap fonts and you may not be able to use them.
But if the fonts are from an older iMac or OS X, then move the fonts to a flash drive, put them on the desktop of your newer iMac, and then double click on them. The built-in program Font Book will open and you’ll see a preview of what the font face looks like and you’ll be able to install it with a click.
You can open Font Book yourself – it’s in your Applications folder – and add Fonts from the File menu. You can preview all of the fonts on your iMac, too. The fonts you added by double clicking on them will be in the “User” collection. You can also delete fonts you don’t use, so if you don’t want to use the fonts you added, you can delete them.
See Apple’s Mac 101 for help on using Font Book.