[GNC] Difficulty in migrating Gnucash to second computer

[Nic Deane]

I am running Gnucash on my desktop computer but when I try to migrate my 
files to my little netbook I can't seem to do it.

I used to do it easily by going to Documents and then copying all the 
gnucash files across. However, under Version: 3.8 Build ID: 
3.8b+(2019-12-29) I don't seem to see any of the familiar gnucash files 
in my Documents folder.

There is an .gnucash hidden file containing 8 items, totalling 45.4 kB  
but not all the files I am used to seeing. The Books folder contains my 
two items 2017 onwards.gnucash.gcm (7.5kb) and Retirement Home 
Accounts.gnucash.gcm (2.5kB).  But, when I try to migrate this directory 
to my netbook all I get is

*'No suitable backend was found for /media/nic/USB 
STICK/.gnucash/books/2017 onwards.gnucash.gcm'*

My desktop is an ACEPC AK2 mini computer running Linux Mint 19.3,  
Cinnamon 4.4.6, Linux kernel 5.0.0-37-generic,  Intel© Celeron© CPU 
J3455 @ 1.50GHz × 4, 7.6 GiB memory.

My netbook is a Samsung NC 110 running Linux Mint 19.3 MATE 1.22.2, 
Intel Atom N2800 @ 1.86 GHz x 4 with 1.9 GiB memory.

Migrating used to be a doddle before but I'm stumped now!

Can you help me?

Many thanks, in advance,

Nic Deane