[Koha] problem with serials

Hi I'm trying to upgrade a koha 2 to koha 3 and i've gone through the basic steps and got most things working - but I'm having a problem with the serials part. I notice from bits of the code that it uses a new table called serialitems but I notice that table for me is blank. Is there a script i'm meant to run to fix this up? or some step I've missed out? Bob