?? Is it not obvious? you cant!!!
I suspect that there is more to this story.. but since you just simplified the question to such an extent.. all I can do is give you the blindingly obvious answer.
You seem to have asked the equivalent of "I put my money in my wallet.. I lost my wallet... how do I get my money back?"
I didn't know if it was possible! My husband back up my iPhone to a friends computer and this computer got crushed and lost everything before I could get my back up!"back"
So, I don't know what to do, my files are very Important to me.
In this case, you may send your computer to some store to fix and check the disk. They may professional to recover the data of the hard disk. Or you can use some software yourself to scan the disk. After that, if you find the iTunes backup files, you can recover the data from iPhone.
I think this bit is Key "iPhone to a friends computer and this computer got crushed ".. which I take to mean
A) Its Crushed
B) its probably in a tip somewhere.. so HDD not accessible
I may be wrong
Cheers
I didn't know if it was possible! My husband back up my iPhone to a friends computer and this computer got crushed and lost everything before I could get my back up!"back"
So, I don't know what to do, my files are very Important to me.
Do you have wifi and did you have iCloud backup on?
If you have backed up your iPhone to PC via iTunes,
the backup should be still kept in your iTunes account,
just log in iTunes in another computer then you can find the data back.
If the backup is damaged,
then try some 3rd party tools to recover.
Good luck!
See more:iPhone recovery FAQ