I'm going to run the aodv-uu on the latest kernel.

Aodv-uu uses a kernel module, which seems to be a conflict.

If I change the kernel module part code, will it work?

aodv-u works with kernel 2.6 and I want to compile from ubuntu 18.04 kernel 4.18

Please advise me if you have ever worked on transferring code from the old kernel to the latest kernel.

You're in for a nightmare.

The changes that have taken place since kernel-2.6 have been considerable. IIRC, they include gcc-3.x --> gcc-8.x; different header arrangements which will really screw you over; rework & patching for several bugs and security loopholes; Whatever refinements (Like Position Independent code, stack protector, etc) that the kernel guys came up with. Many things were axed. That's not an area I follow.

You can go at the compile (patch in your vanished code), and try making it, which will fail. Correct the errors until you see sense.

Alternatively, you could look for old Red Hat or centos code. Some version recently (or perhaps still) in existence ran on a 2.6.32 kernel, heavily patched. Install that instead of your mint or ubuntu. Whatever you want may be there already. Otherwise, look for RH kernel source, and try your luck. If it's EOL, and unavailable, you might be able to torrent it.