Hi.. pls help me how to downgrade my apple ipad i upgrade it to 4.2 version and i lost all my files. before it was 3.2

Typically, Apple doesn't allow you to downgrade the iOS to a prior version. It may allow downgrading during the first week or two after an updated iOS version has been released. After that, you are stuck with the version you have ... eventually being forced to upgrade to a later version for compatibility.

This article should have everything you need.
How to downgrade iOS 8 to iOS 7 1 2

Do you mean upgrade or downgrade ? Because the common version of iOS is now 7.
Maybe this will answer your question:
https://discussions.apple.com/message/19656311

The iPad 3 can be updated to iOS 7. don't use your data bundle, unless you have a unlimited use every month. When you have WiFi, in the settings, click general, then second line update, click that oe and then install now.
When you have iTunes on your computer, connect the iPad. When iTunes starts, it will tell you it has new software for the iPad. Click the tab, download and install.
Itunes is free, the updates are free.

Be aware, update is always at least one version up. NEVER down.
So you won't be able to downgrade the iPad, since iOS 6 was installed. Lower versions, could be downgraded, bacaus you could reset to a low level, and put in a iOS version you should have already downloaded. (I saved most old versions, but they are model specific)

Find data back from iTunes backup because when you have synced your iPhone with iTunes, your iPhone data and files are to be automatically backed up. If you cant access the data or backup file follow http://www.apple.com/iphone/ and Apple Customer Support .

Found this article: http://www.digitaltrends.com/mobile/how-to-downgrade-to-ios-6/

Regret to inform you that the upgrades to IOS7 is non-revertible. by default as Apple has stopped signing the older versions. Once you have upgraded your device to IOS 7 you can not go back to the previous version. However there is a way which is non-recommended by apple but still its a tweak that work. If you still want to do it follow these steps:
Step 1: Download The Proper iOS 6 File
Step 2: Plug The Device Into Your Computer, Cancel The iTunes Automatic Sync Process (If It Starts)
Step 3: Do Not Put Your Device Into DFU Mode, Just Hit Restore
· To put your iPhone in DFU mode:
Hold down the home and power button for 10 seconds.
Release the power button while continuing to hold the home button for eight seconds.
This process sets up your phone automatically for a restore. It is not technically required to downgrade to iOS 6. At the same time, using DFU mode will not have any negative effect on restoring to iOS 6. You can use it if it makes you comfortable.
Once your iPhone is recognized by iTunes, simply hold the Alt/Option button on a Mac or the shift key on a Windows machine and click "Restore iPhone..." The option to choose the iOS6 .ipsw file will pop up, the same way it does when upgrading to iOS 7.

Press Home+Sleep button for few seconds till it shuts down. Later upgrade Iphone to latest firmware through Itunes

If you have an unlocked pghone and whilst on itunes it asks you to update to tht version you must click nor or else it will lock i don't know how to fix this problem you will need to contace apple or get it unlocked again.