Don't worry, it is true that this project isn't worth it. I don't have experience in electronics anyway (though I indeed find this domain interesting).
Yes, they are mainly regular official NES games. They doesn't seem to have been modified, except the "Contra 24 in 1" which obviously has been modified because it shows an URL.
For instance, there is SMB and SMB3 (the ones I would like to backup).
I have a cheap console called "PVP Digital Pocket Light System" (or something similar) that can be found at a low price on ebay.
It allows to play NES games though it doesn't have actual NES hardware: it emulates it. ROMs are stored in a flash memory inside the console.
Is it possible to backup...