I am pretty sure you will need to do a conversion from a Sony ePub to a B&N ePub for them to transfer. ePubs can be generic, but the major players customize the formats to make them readable exclusively on their platforms. They add a form of DRM to protect their rights (not yours) and their hold on your purchasing power.
I believe you will have to find a utility on the internet that allows you to strip off this customization then run it through calibre to recode it for the B&N readers.
There is a site called "makeuseof" on the web at www.makeuseof.com
that writes and publishes a number of "self-help" manuals on many computer related subjects. One such manual is on the program calibre
. Its cheap (free for download) and might be useful to you.
If I am wrong on this, I hope the more educated folks will chime in and provide corrections. I will be sure to learn from them as well.