copy .reg files to a thumbdrive and the product key.
deactivate/remove
Blue Iris product key/license on old machine if you still can.
install/purchase/download Blue Iris from the Blue iris Website.
enter your product key
search for the same version you/re running on old machine.
try importing the Blue Iris .reg file from thumbdrive.
it may be relevant to use the same version level of BI when importing. exporting, as things change over time with versions.
you may need to recreate the Folder tree you had on the other drive(s) if the .reg file or database is pointing to those file name/locations
Like NEW, STORED, Aux 1 Aux2 etc.
This in theory is how it supposed to work,
Wait for other wisdom from some other members in case I missed something.