Power supply failure

Hello,

I have a RNDP600E and it doesn't start.

There seems to be power.

No leds on and nothing happens.

The power supply is a Seasonic SS-300 sfd. It can be replaced because I cannot buy it anymore.

I would like to replace the power supply but I don't know what kind of power supply can be used to replaced it.

Maybe before changing it, fuses can be changed ?

Does someone know what king of tests I can do to test the power supply ?

Does someone know where to buy the same power supply ?

Does someone know if I can get my data by using a new NAS and putting the 6 HDD I have in the new NAS ?

Thanks for your help.

CFOE