GETTING MY GLOCK 43X P80 RAILS TO WORK

I am baffled. I bought a 22lr revolver a couple weeks ago, I planned to lengthen the barrel by about 2 inches so I questioned where by I could buy a alternative barrel on the manufactures Site, they reported that the gun was registered to me from the atf with a certain barrel length and if I transform which i would need a whole new serial variety.B