Power surge fried old base, pairing issues with new base: VTech LS6405

A thunderstorm blew the base to my cordless phone system. I’m convinced that the surge came through the telephone line as the VTech base was the only device to sustain damage even though there were other devices plugged into the same surge suppressor. I’ve purchased a new base set (they come with three handsets), and I’ve replaced the old surge suppressor with one that has a telephone In/Out to prevent something like this from happening again, but I’m having trouble figuring out how to pair my old handsets to the new base.

I always save my User Manuals, so I read through them for both the base and the accessory handsets. Nothing in those manuals addresses how to deregister a handset from a base without using the base. Using the old base is NOT an option as it’s completely nonfunctional in its current state. In addition, because the old base is completely fried, all of the old handsets are displaying an “Out Of Range Or No Pwr At Base” error message. No matter what button I press, I cannot get past this message into the handset menu.

If anyone has any suggestions on how to fix this I’d be super grateful. I really do not want to spend an additional $150 on new handsets over a pairing issue when the old ones work perfectly fine.

A side note: I’m actually pretty good with computer repairs and building/tearing apart a laptop or PC, and I just ordered the parts to repair the Lightning port and replace the battery in my iPhone and feel confident that I’m capable of doing that, but when it comes to repairing other electrical devices, my knowledge is pretty limited (for example, I have zero experience with soldering). I tried to see if I could find where the damage in the old base was but I couldn’t figure it out myself. That being said, I’m willing to learn if someone thinks they can walk me through how and where to look for the problem