Not as difficult as it seems
Download SYS3 QT
Open it and then close it
replace the newly created wallet.dat file with a copy of your saved on and open QT 3 again
Carry out the dunpwallet procedure to generate the file.
Install Spark 4.1.3 and open it and let it sync
Carry out the import wallet procedure
Set a password then backup your new wallet.dat
Done.