How to transmit files from Mac SE into iMac?

IF you have a G3 with floppy(Desktop,AIO,Minitower)then he should be able to read even 800k disks from SE.My 7600/OS 9.1 can do this.
You can also connect this three G3 with a serial printer cable(Mini-DIN 8) and use LocalTalk/filesharing to transport your files.
Second:Depends on the kind of files(Wordprocessor) you use on SE,wether you can really use them on G3.
Merry Christmas

The Mac SE reads/writes files on Diskette 2D in 800K format.
USB diskette drives read/write Diskette HD in 1.4 MB format ONLY.

The Iron Oxide on the two types of diskettes is different, and the format is not interchangeable.

There is some unsupported software on the Apple Download site called LocalTalk/Ethernet Bridge. It could be run on a Mac such as a Platinum-Beige G3 to transfer files between LocalTalk on the Mac SE and Ethernet on the iMac.

There are devices you can buy that support LocalTalk Printers on an Ethernet network. They also support LocalTalk Macs on an Ethernet Network.
AsanteTalk and Farallon EtherPrint LT.

The LocalTalk/Ethernet software from Apple only works up to OS 7.6 and the Mac should not be connected to Internet to work.
Some Hardware bridges don't work with TCP/IP-just as my Dayna Ethernet bridge.

Some Hardware bridges don't work with TCP/IP-just as my Dayna Ethernet bridge.

Good point. That is a serious problem with Mac OS 10.4 and later, which no longer has the ability to do File-Sharing using LocalTalk-over-Ethernet.