Questions about transferring core and USB drives to Nucleus

Roon Core Machine

Windows PC HP Old model

Networking Gear & Setup Details

Tp-Link Router Spectrum Modem

Connected Audio Devices

Current set Up Bluesound Node connected to router via ethernet cable ,

Library Size

on Two Usb Drives ,The My Book is connected directly to Tp-Lnk Router

Description of Issue

I just bought a nucleus and worry that my backup won’t work completely
I Backed up my Library to a USB drive
I plan to connect both my 2tb My Book usb drive(most of My Library in music file) and my easystore
usb drive (some more music files) to The nucleus

why I worry,was I did a backup when my PC hard drive needed to be replaced ,I first tried putting
all the files on the MY Book Eternal Hard Drive,This did not work,all the files I added to the MY Book from the easystore usb ex drive were missing all my edits and personnel

So I had to remove those files and keep them on that second usb drive

since The Nucleus comes with a 1 TB drive ,which isn’t big enough for my whole libary,I will have to stick with adding the two USB drives

I am not sure if I plug the two usb drives after the backup is complete ,or if I do that at the start

Is their a page for editing the paths of the Usb drives? without phone support ,I am afraid some things will get lost,and I added a lot of personal which I can’t replace now,the backup worked last time fine but moving the paths sounds tricky,I understand that I shouldn’t start new paths