Hi, mi rpi3b died, r.i.p, and i was planning to buy a rpi3b+. Can i use the same system i was using in the other?
Or i have to install batocera again?
I had 5.18 and i know it's compatible with rpi3b+
yes, you can without any action.
you can even switch from one arch to an other, for example from rpi2 to rpi3 by unzipping boot.tar.xz on top of the sdcard / usb key and renaming boot/batocera.update to boot/batocera