This is a common problem. There are many forum discussions on here about this. Ignore the different SPARC models (V240 vs V440, etc) they're all the same. Search the forums for the information.
To get you started here are two links to threads that I've been involved in:
If you can't get the right cable I'm sure one of us can find you the pin-outs if you have the means to make one.
Connect the serial cables together then plug that USB to your system.
Be aware that each USB port will be labeled as a different COM port.
Just find the com port in your device manager.
Use terminal emulators like putty and connect via "Serial"
Hit "enter" repeatly if you you get no response or "#." to get to ALOM