I have two sites which can give you some help with Command prompts... The first is Technet from Microsoft and it is quite technical, but includes some help on using the Copy command which you can use to copy files onto a flash drive...
The second is from BleepingComputer and is a bit more helpful in understanding Command prompts in a less technical way:
Unfortunately, it looks like your hard drive may be failing and that means that it is hard to know if you will be able to recover your files... I found reviews on Amazon report a high rate of failure for that drive... It is a hybrid SSD with some conventional hard drive features that allow a larger amount of storage... I suspect it is the SSD part of the hybrid that is still working and the conventional part may be failing or already failed... Do as little as possible with it until you recover your files or you may effectively lose them completely... They might still be recoverable, but only at great expense...
Another option (the external booting option) is here:
You can use the Avira Rescue System option on that page to access your files (if they are still accessible) and copy them to a flash drive... There are still other possibilities that you can use if these do not work... However, please try them first since it is possible that your hard drive may not be capable of doing much more... I would probably start with the Avira Rescue System if it was my computer...
It is very likely that you will need to replace the hard drive in this computer and I suggest going to either a well rated conventional drive or a full SSD drive... The larger SSD drives have come down in price somewhat, so that might be an option... Since you don't have Windows disks, you will probably need to make recovery disks if you have enough access to the drive to do so... Here is a site that may provide some help in creating the disks - note that it may not be possible to do it without access to Windows:
Here is another site with ideas about recovering from the computer not booting... You have already tried a number of these things and I am not sure that it will help, but it may give you more of an idea of what could work:
I have never attempted to create Windows recovery disks from a non-booting computer, so I am not sure that it can be done...
Also, Sony has a diagnostic program which should already be installed in your computer that may be able to tell if the hard drive has failed:
If it doesn't seem to be there, you apparently can download a copy:
Here is their troubleshooting page that may help:
Post back with what you find out after using some of these options and provide as much detail as possible...