I had an older Nokia and got a new one which I needed to upload my phone book to. In order to connect to Nokia 301 from Gammu, plug the phone in with a USB cable and select the "Modem" option on the phone. The others won't work.
Wammu is a GTK frontend to Gammu. You can use for various tasks, but I found that restoring my backup through Wammu failed (even though the file was created with Wammu), while using the commandline tool Gammu directly worked.
Firstly, use the command "gammu-detect" and find the line that reads something with "Nokia", most likely the first line. It will contain something like:
[gammu] device = /dev/ttyACM3 name = Nokia Nokia_301_Dual_SIM connection = at
Put this info in your file
~/.gammurc. You then use this command to backup a file created from either Wammu or Gammu:
gammu -s 0 restore ~/Desktop/nokia.backup
0 denotes that we are using the 0th section of the configuration file, so if you don't have any other configurations, simply leave the 0.