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Do you want to loose part of your bitcoins?
In every transaction you do new "wallets" are created and stored within your wallet and part of the bitcoins is moved from the original to those addresses to avoid tracking of addresses from outside observers. Those transactions will be lost forever.
If you haven't done any transaction since you made your backup just restore the wallet (make a backup of the new one just in case) and resync transactions, that should do it.
Thanks for your help. finally I use older version of MultiBit Classic to restored my backup file which extension name is .wallet – ahgood – 2017-05-05T10:13:47.013
Do you have any idea what software that is? It doesn't look like any I'm familiar with. It's not Bitcoin Core or anything common. Maybe BitFlier? – Anonymous – 2017-05-17T00:27:41.353