Once you root your android phone & install custom rom, you will loose all Touchwiz launcher (i.e samsung’s original) apps like smemo, sNote etc…
Now How will you open those files which you wrote ? You will get .snb files from android system & to get them you can use File Explorer or File Manager apps.
Once you have .snb file , do as follows –
rename files from .snb to .zip then open in explorer
that will solve your issue. go into the snote folder in the zip file and then the media. the .jpg files will be images of your notes.