@jor2404 It is not possible, there is a version of Recalbox for each card precisely because there is a difference in hardware that requires different drivers.
I recommend you to watch the video below, it's not exactly what you want to do, but your solution is basically to make a copy of the BIOS/ROMS/Saves folders on your Rpi3's SD card, flash the image of the Rpi4, and then copy these folders, similar to what is done in the video:
https://www.youtube.com/watch?v=skeULeTu7p8&list=PL2oNQ0AT7fx2ExiSNrfHUzga5GnogI4sh&index=33&ab_channel=Recalbox